[noinline attribute] add noinline attribute.

Propagate it to SILFunction and use it in PerformanceInliner. We also serialize
and parse the attribute.

rdar://15882816


Swift SVN r19150

lib/SIL/SILPrinter.cpp

@@ -1305,6 +1305,9 @@ void SILFunction::print(llvm::raw_ostream &OS, bool Verbose) const {
   if (isGlobalInit())
     OS << "[global_init] ";
   
+  if (isNoinline())
+    OS << "[noinline] ";
+
   printName(OS);
   OS << " : $";