build: Do not add -g to HOSTCFLAGS

The flag is not unconditionally added to CFLAGS either and the
programs built on the host do not get habitually fed to a debugger.
configure: Detect newer (>=4.1) versions of MinGW32

The MinGW32 project is deprecating its old version macros.
configure: Add -D__USE_MINGW_ANSI_STDIO=1 to CPPFLAGS on MinGW32

This enables a more C99-compliant implementation of printf et al.
build: Merge pthreads/w32threads OBJS declarations
avutil: Add deprecation ifdefs around obsolete intfloat code

This long-deprecated code should disappear at the next version bump.
configure: Move the bz2 and zlib checks below phtreads

There are alternate implementations of those libraries that use pthreads.
configure: Reorder pthreads checks

Some pthreads symbols might be present in libc (as shown on various *BSD)
but not all of them, leading to false positives.

Check for the most common compiler flags before the plain symbol check
to avoid known pitfalls.
doxy: Define a group for libswscale documentation

Uniform the style and eliminate a warning on newer doxygen version..
configure: Detect Solaris libc in an OpenIndiana/illumos compatible way
hdsenc: Avoid integer overflow

Also remove a silly leftover pair of parentheses.

Signed-off-by: Martin Storsjö <martin@martin.st>
hdsenc: Fix an off by one error in an array size check

Signed-off-by: Martin Storsjö <martin@martin.st>
hdsenc: Check the init_file() return code

Signed-off-by: Martin Storsjö <martin@martin.st>
sdp: Check theora colorspace before producing the configuration string

This avoids a memory leak (or having to worry about freeing the
config string) if the colorspace isn't accepted.

Signed-off-by: Martin Storsjö <martin@martin.st>
rtpdec_h264: Check the return value of functions doing allocations

Signed-off-by: Martin Storsjö <martin@martin.st>