* configure.in: If we found X on our own, set C_SWITCH_X_SITE and

* configure.in: If we found X on our own, set C_SWITCH_X_SITE and
LD_SWITCH_X_SITE and assume --with-x11.
Only look for X11 files if we weren't told about a window system
or if we were told to use X11 but not told where.
Search the libraries from the s and/or m files when checking for
functions.

* configure.in: Remove any trailing slashes in prefix and exec_prefix.