[PowerPC] Implement missing ISA 2.06 instructions.

Instructions: fctidu[.], fctiwu[.], ftdiv, ftsqrt are not implemented. Implement
them and add corresponding test cases in this patch.

llvm-svn: 291116
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index d3c8848..05acd25 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -47,7 +47,7 @@
       FCTIDZ, FCTIWZ,
 
       /// Newer FCTI[D,W]UZ floating-point-to-integer conversion instructions for
-      /// unsigned integers.
+      /// unsigned integers with round toward zero.
       FCTIDUZ, FCTIWUZ,
 
       /// VEXTS, ByteWidth - takes an input in VSFRC and produces an output in