* configure.in: corrected test for libXmu for some systems; added test for
difftime

* app/main.c: use glib ATEXIT macro

* app/text_tool.c: applied gimp-stric-980321-0 (text preview refresh)

* plug-ins/script-fu/script-fu-console.c: don't need to init gtkpreview stuff,
since we don't use them

* plug-ins/script-fu/*: many portability fixes

* plug-ins/pnm/pnm.c: sprintf portability patch

* plug-ins now #define RAND_MAX if needed

* plug-ins/sparkle/sparkle.c: applied gimp-joke-980322-1

-Yosh