* configure.in (signaldirs): Define and add to configdirs for all

	* configure.in (signaldirs): Define and add to configdirs for all
	targets except some specific ones that are known to not support signals.
	Also clean up formatting.
	* gdb.base/Makefile.in (EXECUTABLES):  Remove sigall and signals.
	(signals, sigall):  Remove rules to build.
	* gdb.base/{sigall.c, sigall.exp, signals.c, signals.exp}:
	Moved to new gdb.signals directory.
	* gdb.signals: New test directory.
	* gdb.signals/{Makefile.in, configure.in, sigall.c, sigall.exp,
	signals.c signals.exp}:  New or moved files.