Do not parse hexadecimal floating point literals in C++0x mode because they are
incompatible with user-defined literals, specifically with the following form:

  0x1p+1

The preprocessing-number token extends only as far as the 'p'; the '+' is not
included. Previously we could get away with this extension as p was an invalid
suffix, but now with user-defined literals, 'p' might well be a valid suffix
and we are forced to consider it as such.

This patch also adds a warning in non-0x C++ modes telling the user that
this extension is incompatible with C++0x that is enabled by default
(previously and with other languages, we warn only with a compliance
option such as -pedantic).

llvm-svn: 93135
diff --git a/clang/lib/Lex/Lexer.cpp b/clang/lib/Lex/Lexer.cpp
index d5a4643..d82f8fc 100644
--- a/clang/lib/Lex/Lexer.cpp
+++ b/clang/lib/Lex/Lexer.cpp
@@ -724,7 +724,8 @@
     return LexNumericConstant(Result, ConsumeChar(CurPtr, Size, Result));
 
   // If we have a hex FP constant, continue.
-  if ((C == '-' || C == '+') && (PrevCh == 'P' || PrevCh == 'p'))
+  if ((C == '-' || C == '+') && (PrevCh == 'P' || PrevCh == 'p') &&
+      (!PP || !PP->getLangOptions().CPlusPlus0x))
     return LexNumericConstant(Result, ConsumeChar(CurPtr, Size, Result));
 
   // Update the location of token as well as BufferPtr.