AST: Rename TypeTransform::transformSubMap()

TypeSubstituter's version was called transformSubstitutionMap(),
and it was never being called as a result. Rename the first one
to match.

Author: slavapestov

include/swift/AST/TypeTransform.h

@@ -154,7 +154,7 @@ case TypeKind::Id:
         return *result;
 
       auto subMap = opaque->getSubstitutions();
-      auto newSubMap = asDerived().transformSubMap(subMap);
+      auto newSubMap = asDerived().transformSubstitutionMap(subMap);
       if (newSubMap == subMap)
         return t;
       if (!newSubMap)
@@ -177,7 +177,7 @@ case TypeKind::Id:
       auto subMap = env->getOuterSubstitutions();
       auto uuid = env->getOpenedExistentialUUID();
 
-      auto newSubMap = asDerived().transformSubMap(subMap);
+      auto newSubMap = asDerived().transformSubstitutionMap(subMap);
       if (newSubMap == subMap)
         return t;
       if (!newSubMap)
@@ -259,7 +259,7 @@ case TypeKind::Id:
       }
 
       auto oldSubMap = boxTy->getSubstitutions();
-      auto newSubMap = asDerived().transformSubMap(oldSubMap);
+      auto newSubMap = asDerived().transformSubstitutionMap(oldSubMap);
       if (oldSubMap && !newSubMap)
         return Type();
       changed |= (oldSubMap != newSubMap);
@@ -281,7 +281,7 @@ case TypeKind::Id:
         return fnTy;
 
       auto updateSubs = [&](SubstitutionMap &subs) -> bool {
-        auto newSubs = asDerived().transformSubMap(subs);
+        auto newSubs = asDerived().transformSubstitutionMap(subs);
         if (subs && !newSubs)
           return false;
         if (subs == newSubs)
@@ -1052,7 +1052,7 @@ case TypeKind::Id:
 
   // If original was non-empty and transformed is empty, we're
   // signaling failure, that is, a Type() return from doIt().
-  SubstitutionMap transformSubMap(SubstitutionMap subs) {
+  SubstitutionMap transformSubstitutionMap(SubstitutionMap subs) {
     if (subs.empty())
       return subs;