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.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@153425 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/configure b/configure
index 941d54c..2dfd66d 100755
--- a/configure
+++ b/configure
@@ -16361,7 +16361,7 @@
 ac_compiler_gnu=$ac_cv_cxx_compiler_gnu
 
     ac_save_CXXFLAGS=$CXXFLAGS
-    CXXFLAGS=-pedantic
+    CXXFLAGS+=" -pedantic"
     if test "$cross_compiling" = yes; then
   ac_cv_huge_val_sanity=yes
 else
@@ -19987,7 +19987,7 @@
 int
 main ()
 {
-float f; std::isinf(f)}
+float f; std::isinf(f);
   ;
   return 0;
 }