[NFC] Exported printing query function.

Allow other compilation units to refer to isFunctionSelectedForPrinting
by declaring it extern.  Maybe at some point it might be nice to put
this into a header related to printing.

Author: nate-chandler

lib/SILOptimizer/PassManager/PassManager.cpp

@@ -167,7 +167,7 @@ static llvm::cl::opt<DebugOnlyPassNumberOpt, true,
               llvm::cl::location(DebugOnlyPassNumberOptLoc),
               llvm::cl::ValueRequired);
 
-static bool isFunctionSelectedForPrinting(SILFunction *F) {
+bool isFunctionSelectedForPrinting(SILFunction *F) {
   if (!SILPrintFunction.empty() && SILPrintFunction.end() ==
       std::find(SILPrintFunction.begin(), SILPrintFunction.end(), F->getName()))
     return false;