[gradient] svg round-trip (i.e. save what it loads)

export is implemented in the base class, but currently only activated
for the SVG export, not for shape export
gradient can also be referenced by style="fill:url(#x)" now
[gradient] svg: stop-(color|opacity) from style and gradientTransform

Now stop-color and stop-opacity are read by dia_svg_parse_style() not only
for our own SVG round-trip. Also included initial gradientTransform, not
passed down to DiaPattern yet. Finally some stop-color offset clipping.
svg: fix xmlGetNsProp() for "xlink:href"
svg: respect xml:space="preserve"

w/o it the parsed string is just stripped, it might be necessary to
also replace extra whitespace within the string.
Bigger drop target for integrated UI case (whole notebook space)
[gradient] Use DiaPattern for PDF import, too.
Don't leak matrix in group_destroy_shallow()
[transform] dox and fix typos
svg: improve stroke-dasharray import with odd number of values
[scan-build] Undefined allocation of 0 bytes

Call to 'alloca' has an allocation size of 0 bytes
File: /mnt/Home/with-git/dia/objects/standard/outline.c
Line: 371
[scan-build] Null pointer passed as an argument to a 'nonnull' parameter

chronoline_event.c:268:7: warning: Null pointer passed as an argument to
a 'nonnull' parameter
  if (strchr(events, ',') != NULL) {
      ^      ~~~~~~
[scan-build] Dereference of null pointer

dia_image.c:413:32: warning: Access to field 'image' results in a
dereference of a null pointer (loaded from variable 'image')
  if (gdk_pixbuf_get_has_alpha(image->image)) {
dox: fix copy&paste bug
Fix path to libEMF emf.h

All libEMF headers are in a libEMF subdir but that bdir does not
appear to be needed as a separate -I path. Instead of hardcoding
-I/usr/include/libEMF (bad idea to assume /usr as its prefix anyway)
and use "emf.h" via it, just directly check and use "libEMF/emf.h".

https://bugzilla.gnome.org/show_bug.cgi?id=719781

Signed-off-by: Hans Breuer <hans@breuer.org>
[warningectomy] sprinkle xmlChar* casts
svg: plug memory leaks triggered by path-variations.svg
svg: plug memory leaks triggered by gradient-variations.svg

Ooops, every pattern was leaked;)
Updated Slovenian translation
[cleanup] Get rid of ConnectionPoint::last_pos

Makes sizeof(ConnectionPoint)==32, before it was 48.
The single real user diagram_update_connections_object() was easy
to convert with other 'redundant' position information. So one less
extra field to maintain.
Fix (inlined) image related leaks

 - DiaImage::scaled was leaked
 - undo information of dia_object_set_pixbuf() was not freed completely
 - Standard - Image (_Image::pixbuf) was not properly reference counted