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.
Fix oops in character array declaration.
whoops! I shouldn't have left the XX in there!

This was actually something that I had when experimenting
with Debian 6.0 compilation. Sorry that it somehow managed
to get committed to mainline!
Merge pull request #268 from monkeyiq/2013jan/issue-249

whoops! I shouldn't have left the XX in there!
Merge pull request #163 from monkeyiq/2012oct/mimetypes2

Some updates for mime handling from sortsmill
Allow the tab and shift+tab keys to move to the next and previous point
when in the glyph window. The old key bindings are still effective too.
Merge pull request #273 from monkeyiq/2013jan/hotkeys

Allow the tab and shift+tab keys to move to the next and previous point when in the glyph window.
Updates to the cvlayers palette.

+/- buttons are now smaller
Layers label is not shown
Overall horizontal width of palette is smaller
Eyeball icon removed in favour of checkbox
 Horizontal compaction of palette enabled by the above eye->check change.
Merge pull request #274 from monkeyiq/2013jan/issue-250

Updates to the cvlayers palette.
Change the Gdraw.ScreenWidthCentimeters to 60 by default. That is about a 24 inch
monitor and makes things more acceptable on a default Linux desktop.

I thought I'd turned off the mac menu icons before? Anyway, force that setting off
by default.

The OSX bundle script has some new tweaks to set things up for mac laptops.
why care what the setting *was*, only what we want to force it into.
Merge pull request #275 from monkeyiq/2013jan/issue-251

Turn off the Mac menu icons by default
Gdraw.ScreenWidthCentimeters: 100 looks OK on both the 27 hich res screen
and the 23 inch 1080p screen.
Merge pull request #276 from monkeyiq/2013jan/upscreenwidthagain

Gdraw.ScreenWidthCentimeters: 100 looks OK on both the 27 hich res screen
By default open contours are now rendered in a darkish red color.

When you complete a contour by joining back to the starting point then
that path is rendered in a normal color. Advanced users can turn off
this functionality by turning "Off" the preference
Editing/DrawOpenContoursWithHighlight.
Merge pull request #278 from monkeyiq/2013jan/issues/242

By default open contours are now rendered in a darkish red color.
Change Contours -> Paths throughout
Merge pull request #279 from monkeyiq/2013jan/issues/242v2

Change Contours -> Paths throughout
revert Gdraw.ScreenWidthCentimeters to 34 from earlier today.