clang-format: Improve expression heuristics.

Upon encountering a binary operator inside parentheses, assume that the
parentheses contain an expression.

Before:
  MACRO('0' <= c&& c <= '9');

After:
  MACRO('0' <= c && c <= '9');

llvm-svn: 212040
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index 11a42a5..75eea98 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -4841,6 +4841,7 @@
   verifyIndependentOfContext("MACRO(int *i);");
   verifyIndependentOfContext("MACRO(auto *a);");
   verifyIndependentOfContext("MACRO(const A *a);");
+  verifyIndependentOfContext("MACRO('0' <= c && c <= '9');");
   // FIXME: Is there a way to make this work?
   // verifyIndependentOfContext("MACRO(A *a);");