Make the intltool take care of appdata file

The synfigstudio.appdata.xml.in is ready, but the content in it should be
improved if needed.
Set the border relief style of close button of canvas window tab to None
Add two new icons

Add show and snap guide line icons
Add a new screenshot of 0.64.0 for using in Appdata.xml

Add a new screenshot accroding to the spec of appdata, 16:9 (1360x768)
Show icon only for panel toolbar on all platforms
Added target png_spritesheet

png_spritesheet is a target to put all frames in a single png file.
The frames are drawn vertically below each other.

I think it's a good start for this feature request:
http://www.synfig.org/issues/thebuggenie/synfig/issues/222
Although not everything wished there is implemented.

It's only a modification of the target png, there is no way to set the
space between two frames or to draw them horizontally.

Anyway it's useful for me and, I'm sure, for many others.
Fix description of png_spritesheet target. Cleanup.
Portability fixes for OpenBSD. Patch by Aaron Suen.
synfig-core/configure.ac: Squeeze some if-else blocks into equivalent AM_CONDITIONAL blocks.
synfig-core/configure.ac: Replace manual help strings with AS_HELP_STRING.
synfig-core/configure.ac: Take out if-else block that I forgot.
synfig-core/configure.ac: Shorten help strings.
synfig-core/configure.ac: Erase commented-out code.  They can be rewritten if we need them.
synfig-core/configure.ac: Erase lonely 'true' that did nothing.
synfig-core/configure.ac: Turn mixed indentation (tabs+spaces) into just tabs.
synfig-core/configure.ac: Erase more commented-out code.
synfig-core/configure.ac: Line up arguments to AC_CHECK_LIB dlopen.
Update Linux build script for Ubuntu 13.10
Typos
BugFix Canvas Metadata blank for new canvases #125

- Add workarea::have_meta_data with minimal test presence of grid_size and grid_show
- Create from default value if no have meta data