Add some fixes to the configure script  for isInf and add
--enable-libcpp to projects/sample.

Patch by Dmitri Shubin with additional fixes by me.

llvm-svn: 153425
diff --git a/llvm/projects/sample/Makefile.llvm.rules b/llvm/projects/sample/Makefile.llvm.rules
index 7467d84..6e04724 100644
--- a/llvm/projects/sample/Makefile.llvm.rules
+++ b/llvm/projects/sample/Makefile.llvm.rules
@@ -245,6 +245,11 @@
   endif
 endif
 
+ifeq ($(ENABLE_LIBCPP),1)
+  CXX.Flags +=  -stdlib=libc++
+  LD.Flags +=  -stdlib=libc++
+endif
+
 ifeq ($(ENABLE_PROFILING),1)
   BuildMode := $(BuildMode)+Profile
   CXX.Flags := $(filter-out -fomit-frame-pointer,$(CXX.Flags)) -pg -g