* dbxout.c: Remove unnecessary #undefs.
(GDB_INV_REF_REGPARM_STABS_LETTER, DBX_MEMPARM_STABS_LETTER)
(FILE_NAME_JOINER, STABS_GCC_MARKER): Remove; fold sole
definition into use sites.
(cwd): Make local to dbxout_init.
(dbxout_init): Restructure cwd-using logic for clarity. Use
IS_DIR_SEPARATOR.
* xcoffout.h (DBX_OUTPUT_GCC_MARKER): Definition of
STABS_GCC_MARKER folded in here.
* system.h: Poison now-unused macros.
* doc/tm.texi: Remove documentation of now-unused macros.
From-SVN: r89387
