Fixup diagnostics around type(of:) and dynamicType handling

Be laxer about the parsing for type(of:) so as not to get in the way of
other declarations that may use ‘type’ as their base name.

lib/Basic/StringExtras.cpp

@@ -36,7 +36,6 @@ bool swift::canBeArgumentLabel(StringRef identifier) {
 
 bool swift::canBeMemberName(StringRef identifier) {
   return llvm::StringSwitch<bool>(identifier)
-    .Case("dynamicType", false)
     .Case("init", false)
     .Case("Protocol", false)
     .Case("self", false)