[Macros] Remove ModuleDecl::isInGeneratedBuffer.

This method was misleading. The majority of callers (all but one!) don't want
to unconditionally treat all locations in any macro expansion buffer the
same way, because the code also must handle nested macro expansions. There
is one part of SourceKit (and possibly others) that really do want to ignore
all macro expansions, but those can be handled within SourceKit / IDE code,
because I don't believe this utility is useful in the frontend.

lib/AST/Module.cpp

@@ -816,13 +816,6 @@ SourceFile *ModuleDecl::getSourceFileContainingLocation(SourceLoc loc) {
   return foundSourceFile;
 }
 
-bool ModuleDecl::isInGeneratedBuffer(SourceLoc loc) {
-  SourceFile *file = getSourceFileContainingLocation(loc);
-  if (!file)
-    return false;
-  return file->Kind == SourceFileKind::MacroExpansion;
-}
-
 std::pair<unsigned, SourceLoc>
 ModuleDecl::getOriginalLocation(SourceLoc loc) const {
   assert(loc.isValid());