Add a MCAsmInfoELF class and factor some code into it.

We had a MCAsmInfoCOFF, but no common class for all the ELF MCAsmInfos before.

llvm-svn: 192760
diff --git a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp
index 91578a9..f3dddce 100644
--- a/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp
+++ b/llvm/lib/Target/PowerPC/MCTargetDesc/PPCMCAsmInfo.cpp
@@ -46,8 +46,7 @@
   CommentString = "#";
   GlobalPrefix = "";
   PrivateGlobalPrefix = ".L";
-  WeakRefDirective = "\t.weak\t";
-  
+
   // Uses '.section' before '.bss' directive
   UsesELFSectionDirectiveForBSS = true;