Remove all uses of C_DEBUG_SWITCH and LIBS_DEBUG.

Remove all uses of C_DEBUG_SWITCH and LIBS_DEBUG.
* s/usg5-4.h (LIBS_DEBUG):
* s/irix6-5.h (C_DEBUG_SWITCH):
* s/gnu-linux.h (LIBS_DEBUG):
* s/darwin.h (LIBS_DEBUG):
* s/bsd-common.h (LIBS_DEBUG):
* s/aix4-2.h (LIBS_DEBUG, C_DEBUG_SWITCH):
* m/iris4d.h (LIBS_DEBUG):
* m/hp800.h (LIBS_DEBUG): Remove definitions.

* Makefile.in (LIBES): Remove reference to LIBS_DEBUG.
(LIBS_DEBUG): Remove definition.

* configure.in: Remove all references to C_DEBUG_SWITCH.