[clang] Register isConstexpr matcher

This diff registers isConstexpr matcher.

Test plan:
make check-all
check that "match varDecl(isConstexpr())" 
works in clang-query

Differential revision: https://reviews.llvm.org/D32112

llvm-svn: 300427

clang/lib/ASTMatchers/Dynamic/Registry.cpp

@@ -296,6 +296,7 @@ RegistryMaps::RegistryMaps() {
   REGISTER_MATCHER(isCatchAll);
   REGISTER_MATCHER(isClass);
   REGISTER_MATCHER(isConst);
+  REGISTER_MATCHER(isConstexpr);
   REGISTER_MATCHER(isConstQualified);
   REGISTER_MATCHER(isCopyAssignmentOperator);
   REGISTER_MATCHER(isCopyConstructor);