Simplify.
Fix style.
Fix build with --disable-everything --enable-perl.
Define iconFile resource independently of BG_IMAGE_FROM_FILE.
Revise preprocessor macros that control the core bg image code.

Move definition of BG_IMAGE_FROM_FILE in rxvt.h and add analogous
BG_IMAGE_FROM_ROOT macro that is set if the code to manage the root
pixmap is needed.
Make code needed to set the bg pixmap conditional to HAVE_IMG.
Properly manage BG_IS_TRANSPARENT flag in core bg image code.
Destroy bg_img directly rather than through bg_destroy.
Move destruction of bg_img out from bg_destroy.
Fix last change to rxvtperl.xs.
Simplify reset of bg_flags.
Simplify.
Simplify.
Update/reword comment.
Move check for mapped status in bg_render.
Get rid of BG_IS_VALID flag.
Set root_img only when transparency is requested and replace tests on
the transparency option with (more accurate) tests on root_img.
Inline two methods in their callers.
Simplify.
Update Changes.