Builds on the work Dylan Baker did for glproto. Note that this does
not produce _quite_ identical pc files as the autotools build, but it
only affects the name and description strings which are only informative
anyway.

Just to be petty:

% time ( ./configure --prefix=/tmp/xorgproto && make install; ) >& /dev/null
2.42s user 1.67s system 107% cpu 3.804 total

% time ( meson setup build && meson configure build -Dprefix=/tmp/xorgproto && ninja -C build install ) >& /dev/null
0.55s user 0.11s system 100% cpu 0.658 total

Signed-off-by: Adam Jackson <ajax@redhat.com>