Add script to install build depend for Debian

Add a script debian/deb-build-dep. The script parses debian/control file
and installs the necessary build time dependent packages to the system:

   $ sudo ./debian/deb-build-dep
Debian package: fontforge conflict fontforge-nox

remove sugguestion to install both.
Add task notes.
Stop changing a const char* argument to SFGetChar.
Annotate glyph search functions.
Add notes.
A first try at layer reading for u.f.o..
Add declarations.
Fix many things.
Merge pull request #1118 from JoesCat/master

Additional improvement towards 'make dist'
Fix build for glib < 2.28
Merge pull request #1121 from abelcheung/master

Fix build for glib < 2.28
AT_TESTED only checks for programs in existing path. Not only is this unuseful in test suite, it actually causes the whole test suite fail to run under clean environments (such as chroot)
Merge pull request #1123 from abelcheung/201401-build-fixes

Disable AT_TESTED in testsuite
Merge pull request #1029 from mozbugbox/install-debian-depends

Add script to install build depend for Debian
Be more permissive about text objects in input.
Install xdg desktop stuff if xdg utilities are found
Merge pull request #1125 from abelcheung/201401-build-fixes

Install xdg desktop stuff if xdg utilities are found
Merge branch 'master' into ufo_layer_1
Merge pull request #1127 from fontforge/ufo_layer_1

Add multiple layer import to the u.f.o. driver.