The install target guessed the module directory from whichever immodule
was already installed when pkg-config had nothing to say — a guess that
finds nothing on a fresh system and needed seven lines of README to
explain. It uses GTK's own pkg-config variables now, or the
GTK_MODULE_DIR a packager sets. The README also loses a negation about
a font argument that no longer exists and two paragraphs that repeat the
dependency list.
Only ibus.o needs the D-Bus and xkbcommon flags, so give them the same
per-object scoping as the popup and XIM objects. The docker targets used
-B, which recursive makes inherit: the daemon was linked three times and
the live tests built twice per docker-check. gtk/Makefile repeated the
module-directory check and cache refresh in install and uninstall.
