clang-format: Fix post-commit review comment of r299204, use Style.isCpp().

Also, while at it, s/IsCpp/isCpp/ so that it follows LLVM style.

llvm-svn: 299214
diff --git a/clang/lib/Format/FormatTokenLexer.cpp b/clang/lib/Format/FormatTokenLexer.cpp
index 90b80a4..91c9af0 100644
--- a/clang/lib/Format/FormatTokenLexer.cpp
+++ b/clang/lib/Format/FormatTokenLexer.cpp
@@ -560,7 +560,7 @@
     Column = FormatTok->LastLineColumnWidth;
   }
 
-  if (Style.IsCpp()) {
+  if (Style.isCpp()) {
     if (!(Tokens.size() > 0 && Tokens.back()->Tok.getIdentifierInfo() &&
           Tokens.back()->Tok.getIdentifierInfo()->getPPKeywordID() ==
               tok::pp_define) &&