Revert "Make sure that we do not try to create shared versions of stdlib_binary_only functions when specializing."

This reverts commit r26001; it broke validation-tests/stdlib/String.swift

Swift SVN r26005

lib/SILPasses/Utils/Generics.cpp

@@ -147,7 +147,7 @@ void dumpTypeSubstitutionMap(const TypeSubstitutionMap &map) {
 
 /// Check if we can clone and remap types this function.
 static bool canSpecializeFunction(SILFunction *F) {
-  return !F->isExternalDeclaration() && F->canHaveSharedLinkage();
+  return !F->isExternalDeclaration();
 }
 
 bool