On DEC OSF/1 use x-dec-osf1 for xmake-file

From-SVN: r2315

gcc/config/mips/x-dec-osf1

+# Define CC and OLDCC as the same, so that the tests:
+#	if [ x"$(OLDCC)" = x"$(CC)" ] ...
+#
+# will succeed (if OLDCC != CC, it is assumed that GCC is
+# being used in secondary stage builds).  We need to pass
+# the -Wf,-XNg1500 option so the compiler can compile the
+# G++ file cp-parse.c.  Otherwise it complains about
+# too many case statements.  -Olimit is so the user
+# can use -O2.  Down with fixed size tables!
+
+CC		= $(OLDCC)
+OPT		= -O1
+OLDCC		= cc -Wf,-XNg1500 -Olimit 3000 $(OPT)
+INSTALL		= installbsd -c
+
+# The bison output files are machine-indep,
+# so different flags for a particular machine are not useful.
+#BISONFLAGS	= -l