[SystemZ] Add missing arithmetic instructions

This adds the remaining general arithmetic instructions
for assembler / disassembler use.  Most of these are not
useful for codegen; a few might be, and those are listed
in the README.txt for future improvements.

llvm-svn: 302665
diff --git a/llvm/lib/Target/SystemZ/README.txt b/llvm/lib/Target/SystemZ/README.txt
index 86a1322..74cf653 100644
--- a/llvm/lib/Target/SystemZ/README.txt
+++ b/llvm/lib/Target/SystemZ/README.txt
@@ -63,7 +63,7 @@
 
 --
 
-We don't use ICM or STCM.
+We don't use ICM, STCM, or CLM.
 
 --