[PowerPC] 32-bit ELF PIC support

This adds initial support for PPC32 ELF PIC (Position Independent Code; the
-fPIC variety), thus rectifying a long-standing deficiency in the PowerPC
backend.

Patch by Justin Hibbits!

llvm-svn: 213427
diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.h b/llvm/lib/Target/PowerPC/PPCSubtarget.h
index 96d3d62..58314538 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.h
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.h
@@ -222,6 +222,9 @@
   /// isBGQ - True if this is a BG/Q platform.
   bool isBGQ() const { return TargetTriple.getVendor() == Triple::BGQ; }
 
+  bool isTargetELF() const { return TargetTriple.isOSBinFormatELF(); }
+  bool isTargetMachO() const { return TargetTriple.isOSBinFormatMachO(); }
+
   bool isDarwinABI() const { return isDarwin(); }
   bool isSVR4ABI() const { return !isDarwin(); }