Support fileprivate access level to be usableFromInline.

This is needed for cross-module-optimization.
So far only internal and private was supported.

Author: eeckstein

lib/AST/Decl.cpp

@@ -3115,7 +3115,7 @@ static AccessLevel getAdjustedFormalAccess(const ValueDecl *VD,
     return getMaximallyOpenAccessFor(VD);
 
   if (treatUsableFromInlineAsPublic &&
-      (access == AccessLevel::Internal || access == AccessLevel::Private) &&
+      access <= AccessLevel::Internal &&
       VD->isUsableFromInline()) {
     return AccessLevel::Public;
   }