Add a polymorphic AST matcher for testing whether a constructor or a conversion declaration is marked as explicit or not.

llvm-svn: 244666
diff --git a/clang/lib/ASTMatchers/Dynamic/Registry.cpp b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
index 7e3df2d..be04ed4 100644
--- a/clang/lib/ASTMatchers/Dynamic/Registry.cpp
+++ b/clang/lib/ASTMatchers/Dynamic/Registry.cpp
@@ -249,6 +249,7 @@
   REGISTER_MATCHER(isDefinition);
   REGISTER_MATCHER(isDeleted);
   REGISTER_MATCHER(isExceptionVariable);
+  REGISTER_MATCHER(isExplicit);
   REGISTER_MATCHER(isExplicitTemplateSpecialization);
   REGISTER_MATCHER(isExpr);
   REGISTER_MATCHER(isExternC);