Feature/lib xft option

[nbuwe]

Move libXft glue to a separate module.

This brings the xlib glue back to the state it was in before the merge of 'doublec/linux_fonts' (modulo cleaning up a duplicate #include), with all the new xft code in its own files and included in all the right places.

I haven't yet figured out the subparts part of it so xft_wrappers.self is not loaded.

By default Xft is not enabled for now, you need to -DSELF_XFT=ON when configuring the build dir.

Review and feedback are appreciated.

[nbuwe]

A bit unrelated, but for the record - on a typical x86_64 linux machine with 32-bit support installed you should be able to configure the build dir with something like:

(export CC='cc -m32 -no-pie -fno-pie'; \
 export CXX='c++ -m32 -no-pie -fno-pie'; \
 export PKG_CONFIG_PATH='/usr/lib/i386-linux-gnu/pkgconfig:/usr/share/pkgconfig'; \
 export PKG_CONFIG_LIBDIR='/usr/lib/i386-linux-gnu'; \
 export PKG_CONFIG_SYSROOT_DIR='/'; \
 time cmake -B build-debug-xft -DSELF_XFT=ON -DCMAKE_BUILD_TYPE=Debug .)

and get all the magic flags right automatically.

[nbuwe]

As an aside, stuff like

set(SELF_X11_INIT ON)

in platform files doesn't seem to work, b/c platform files are included too late, I think. But that was not the red herring I was looking for, so I didn't try to address it in any way.

[russellallen]

common.cmake is setting SELF_X11_INIT - I'm not sure why the platform files also have it, they are included too late. I should remove that line from each platform file to reduce confusion.

[nbuwe]

I would imagine the intention might be to let platforms change the default. So, say, weirdix.cmake could set(SELF_X11_INIT OFF). I'm not sure if that level of super-flexibility is actually needed or wanted.

(OTOH, adding -m32 and warning to set pkg-config path variables might be a good and useful thing to do on 64-bit hosts I think).