Merge pull request #1246 from rrthomas/master

Garbage collection and other goodness
configure.ac: remove test for C++ compiler: we have no C++
Remove Caps-as-Alt setting: this is for desktops to do, not apps
Make Python mandatory.
Remove traces of libspiro being optional (it is now mandatory)
Remove undocumented support for selecting UFO v1 output at build time
Remove undocumented unconfigurable NATIVE_CALLBACKS define
Remove undocumented unconfigurable NOPLUGIN define
scripting.c: add some missing initializers
Remove another little trace of VMS
Fix an unused parameter warning
Remove manual library/executable version checking; use the linker + semantic versioning
Distribute all sources, no sense not doing so.
Always use double, not float, for real type
Remove unused configure flag --disable-link-test
Make Fontforge script mandatory
Require giflib, libjpeg, libpng and libtiff
Expand building instructions, fixing issue #1218
Fix gnulib (and hence libgc) linking issues for platforms that need more of it (e.g. mingw)
tests/Makefile.am: add MAINTAINERCLEANFILES so that .gitignore is correctly generated