Readline: Cleanup some warnings

Readline: Cleanup some warnings

Cleanup the readline warnings that gdb buildbot complains about.

To prevent wcwidth missing declaration warnings, add the SOURCE /
EXTENSION macros to config.in that have already checked for in
configure.

Ensure pid is a long before printing as one.  Also fix GNU style.

Check the return value of write the same way as history_do_write ().

These changes are consistent with upstream readline.

readline/ChangeLog.gdb:

	* config.h.in: Add SOURCE/EXTENSION macros.
	* histfile.c (history_truncate_file): Check return of write.
	* util.c (_rl_tropen): Ensure pid is long.