Now builds on x86_64 and via portable C distribution.

Now builds on x86_64 and via portable C distribution.

The build process now builds FFIs after it build-bands.  An FFI's
"build" target now combines the old "generate" and "build" targets,
and knows from its host whether to compile-liarc-bundle.  The
"install" target also knows whether to install-liarc-bundle.

Building the FFIs after build-bands means we can use src/microcode/
scheme and src/lib.  Compiling the .scm after building the shim
ensures that the .scm's FFI syntax and the shim are consistent.

* doc/gtk/gtk.texinfo (Installation): Updated, with a section about
building the portable C distribution.  Replaced "smallexample" with
"example" because of the former's smaller font.

* src/Makefile.in (build-ffis): This new target is needed in src/etc/
make-liarc.sh, and now appears after build-bands in most contexts.
Moved ffi from LIARC_BOOT_BUNDLES, and FFIS from LIARC_BUNDLES, but
not INSTALLED_SUBDIRS.

* src/configure.ac: Simplified the with-gtk default, which can expect
a host with an FFI after build-bands.  Just test for Gtk 2.0 libraries
via pkg-config.

* src/etc/compile.scm (compile-ffi): Use in-liarc; delay C compilation.

* src/etc/make-liarc.sh: Add build-ffis after build-bands.

* src/gtk/Makefile-fragment: Combine generate and build into one, and
use ../microcode/scheme.

* src/gtk/gtk-shim.h: Replace "ulong" with "unsigned long".

* src/gtk/gtkio.c.stay: Make run_gtk's definition agree with its
declaration, and explicitly cast to select_registry_t.