[Bug: 21.5-b27] describe-function shows build-time file locations

[Stephen J. Turnbull]

Ron Isaacson writes:

 > I notice that describe-function mistakenly reports the build-time
 > location for some functions.

XEmacs is correct, you are wrong.  Those files were in fact loaded at
build time.  At least, custom.elc is.

 > even exist. The function is loaded correctly of course, and M-x
 > find-library custom RET takes me to the right place, but M-x
 > find-function defface RET tells me:
 > 
 >   The library "/var/tmp/build.ronisaac/xemacs/core/21.5.27/ia32.linux.2.4.glibc.2.3/gcc32/lisp/custom" is not in the path.

I'm not sure what's going on with this.  I'll take a look.

Note that the semantics of these functions is not at all clear.
Originally the intention was to take you to where you can edit the
function to change the behavior of XEmacs.  For a dumped file that
should be a file in the source tree.  That's arguably inconvenient in
your environment, but we have to be careful to find the source file in
cases where it does exist.  (I say "arguably" because we often get
reports that somebody has edited and compiled a Lisp file, but the
change doesn't "take" because it's a dumped file, so the changed .elc
needs to be reloaded in every session.)