mmx: Document implementation(s) of pix_multiply().

I look at that function and can never remember what it does or how it
manages to do it.
Use AC_LINK_IFELSE to check if the Loongson MMI code can link

The Loongson code is compiled with -march=loongson2f to enable the MMI
instructions, but binutils refuses to link object code compiled with
different -march settings, leading to link failures later in the
compile. This avoids that problem by checking if we can link code
compiled for Loongson.

Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Markos Chandras <markos.chandras@imgtec.com>
Make use of image flag in noop iterators

Similar to c2230fe2aff, simply check against SAMPLES_COVER_CLIP_NEAREST
instead of comparing all the x/y/width/height parameters.
Add ITER_SRC and ITER_DEST iter flags

These indicate whether the iterator is for a source or a destination
image. Note iterator initializers are allowed to rely on one of these
being set, so they can't be left out the way it's generally harmless
(aside from potentil performance degradation) to leave out a
particular fast path flag.
Add ITER_WIDE iter flag

This will be useful for putting iterators into tables where they can
be looked up by iterator flags. Without this flag, wide iterators can
only be recognized by the absence of ITER_NARROW, which makes testing
for a match difficult.
Always set the FAST_PATH_NO_ALPHA_MAP flag for non-BITS images

We only support alpha maps for BITS images, so it's always to ignore
the alpha map for non-BITS image. This makes it possible get rid of
the check for SOLID images since it will now be subsumed by the check
for FAST_PATH_NO_ALPHA_MAP.

Opaque masks are reduced to NULL images in pixman.c, and those can
also safely be treated as not having an alpha map, so set the
FAST_PATH_NO_ALPHA_MAP bit for those as well.
noop: Keep information about iterators in an array of pixman_iter_info_t

Instead of having a nest of if statements, store the information about
iterators in a table of a new struct type, pixman_iter_info_t, and
then walk that table when initializing iterators.

The new struct contains a format, a set of image flags, and a set of
iter flags, plus a pixman_iter_get_scanline_t, a
pixman_iter_write_back_t, and a new function type
pixman_iter_initializer_t.

If the iterator matches an entry, it is first initialized with the
given get_scanline and write_back functions, and then the provided
iter_initializer (if present) is run. Running the iter_initializer
after setting get_scanline and write_back allows the initializer to
override those fields if it wishes.

The table contains both source and destination iterators,
distinguished based on the recently-added ITER_SRC and ITER_DEST;
similarly, wide iterators are recognized with the ITER_WIDE
flag. Having both source and destination iterators in the table means
the noop_src_iter_init() and noop_dest_iter_init() functions become
identical, so this patch factors out their code in a new function
noop_iter_init_common() that both calls.

The following patches in this series will change all the
implementations to use an iterator table, and then move the table
search code to pixman-implementation.c.
sse2: Replace the fetcher_info_t table with a pixman_iter_info_t table

Similar to the changes to noop, put all the iterators into a table of
pixman_iter_info_t and then do a generic search of that table during
iterator initialization.
mmx: Replace the fetcher_info_t table with a pixman_iter_info_t table

Similar to the SSE2 commit, information about the iterators is stored
in a table of pixman_iter_info_t.
fast: Replace the fetcher_info_t table with a pixman_iter_info_t table

Similar to the SSE2 and MMX patches, this commit replaces a table of
fetcher_info_t with a table of pixman_iter_info_t, and similar to the
noop patch, both fast_src_iter_init() and fast_dest_iter_init() are
now doing exactly the same thing, so their code can be shared in a new
function called fast_iter_init_common().
general: Store the iter initializer in a one-entry pixman_iter_info_t table

In preparation for sharing all iterator initialization code from all
the implementations, move the general implementation to use a table of
pixman_iter_info_t.

The existing src_iter_init and dest_iter_init functions are
consolidated into one general_iter_init() function that checks the
iter_flags for whether it is dealing with a source or destination
iterator.

Unlike in the other implementations, the general_iter_init() function
stores its own get_scanline() and write_back() functions in the
iterator, so it relies on the initializer being called after
get_scanline and write_back being copied from the struct to the
iterator.
Add _pixman_implementation_iter_init() and use instead of _src/_dest_init()

A new field, 'iter_info', is added to the implementation struct, and
all the implementations store a pointer to their iterator tables in
it. A new function, _pixman_implementation_iter_init(), is then added
that searches those tables, and the new function is called in
pixman-general.c and pixman-image.c instead of the old
_pixman_implementation_src_init() and _pixman_implementation_dest_init().
Delete the old src/dest_iter_init() functions

Now that we are using the new _pixman_implementation_iter_init(), the
old _src/_dest_iter_init() functions are no longer needed, so they can
be deleted, and the corresponding fields in pixman_implementation_t
can be removed.
Consolidate all the iter_init_bits_stride functions

The SSE2, MMX, and fast implementations all have a copy of the
function iter_init_bits_stride that computes an image buffer and
stride.

Move that function to pixman-utils.c and share it among all the
implementations.
configure.ac: Don't use '+=' since it's not POSIX

Reviewed-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Matthieu Herrb <matthieu.herrb@laas.fr>
Require GTK+ version >= 2.16

I'm got bug in my system:

lcc: "scale.c", line 374: warning: function "gtk_scale_add_mark" declared
          implicitly [-Wimplicit-function-declaration]
      gtk_scale_add_mark (GTK_SCALE (widget), 0.0, GTK_POS_LEFT, NULL);
      ^

  CCLD   scale
scale.o: In function `app_new':
(.text+0x23e4): undefined reference to `gtk_scale_add_mark'
scale.o: In function `app_new':
(.text+0x250c): undefined reference to `gtk_scale_add_mark'
scale.o: In function `app_new':
(.text+0x2634): undefined reference to `gtk_scale_add_mark'
make[2]: *** [scale] Error 1
make[2]: Target `all' not remade because of errors.

$ pkg-config --modversion gtk+-2.0
2.12.1

The demos/scale.c use call to gtk_scale_add_mark() function from 2.16+
version of GTK+. Need do support old GTK+ (rewrite scale.c) or simple
demand of high version of GTK+, like this:
Merge branch 'master' of git://anongit.freedesktop.org/git/pixman