Use the mime type to sniff what type of image we have instead of using the extension.

Brings in:
https://github.com/sortsmill/fontforge/commit/373ff5af95b1511560d37c7b498142cc7e8a9d51

This is only the top commit, it seems best to dig back to:
0a0bb72b5da3d6aaec893f68fbe7440fce2c2eae
Bringing in some stuff from the previous two commits, back to
0a0bb72b5da3d6aaec893f68fbe7440fce2c2eae
from the sortsmill.
[Fontforge-devel] absolute-FREETYPE_SOURCE.patch, 2012sep17
Don’t highlight menu separators when selected, 7638f27, 2012dec22
Update the timestamps which are shown in about dialogs.

The timestamps are now generated during the configure run. If there is
a .git directory then the git hash is taken and shown in the console
at startup and also in the about window.

To compliment things, perhaps the "release" number should be shown in
both places too. So if a user is running version 2.1.0 then they will
know that.

MacFontForgeApp.zip is also no longer modified, instead a new
MacFontForgeAppBuilt.zip is created on MacOS builds.
Updated unix build instructions.
Merge pull request #193 from Arthaey/master

Updated unix build instructions.
Merge pull request #192 from monkeyiq/2013jan/update-build-times-and-show-git-hash

Update the timestamps which are shown in about dialogs.
Added more dependencies for building under *nix.
Fix crash with contextual ligatures in feature file

When adding looks for contextual ligatures added only marked glyphs as
components, so “sub a' b' c d by a_b;” should add a ligature with “a b”
components not “a b c d”.

The crash was simply because the string was allocated the correct size
but too much was copied into it.

Reported in FontForge mailing list:
http://sourceforge.net/mailarchive/message.php?msg_id=30291884
Merge pull request #194 from Arthaey/master

Added more dependencies for building under *nix.
Default pixmaps are now tango. Old pixmaps retained as the 2012 theme.

Expanded out the zip files for pixmaps. Simpler to have them in
directories of their own and the build system not expand zips or
whatnot. Whichever theme you select is the one that the pixmaps will
be installed for. All pixmaps are shipped in the tarball.

Added macports Portfile for central keeping: This is the golden copy
of the file and should always be considered the latest. All my other
fontforge Portfile files just softlink to this golden copy.
Some nice fonts for a font program!
new function to find pixmap dir
try to load the resources file form the pixmap dir if there is no set theme.
hush
Merge pull request #195 from monkeyiq/2013jan/themecleanup

Default pixmaps are now tango. Old pixmaps retained as the 2012 theme.
When the metricsview is open and the user decides to draw a shape in the
class of a rectangle (cvshape) then suspend live updates to the metricsview
until the shape has been completed (ie, the mouse button released).

Something is treading on its own feet in the live update process here. The
core of that is triggered by MVRegenChar() in the two lines of BDFCharFree()
followed by NULLing the mv->show->glyphs[sc->orig_pos]. If those lines happen
then the shape is no longer drawn properly in the active charview and things
are generally not what the user expects.
Merge pull request #198 from monkeyiq/2013jan/metricsview-rect-render-issue

When the metricsview is open allow things like rectangles to still be drawn in the charview.
Allow "no glyphs" check in TTF save to see glyph 0
Corrects issue in which a font with exactly one glyph, no ".notdef", generates
a spurious "no glyphs" warning on Generate of TTF or OTF.
Fix apparent typo in call to utf82u_strncpy.

The original author must have meant ubuf+1 and not ubuf-1, in order to
preserve the space previously inserted at index 0 of ubuf[].