Rework HeaderSearch's interface for getting a module from a name and

for getting the name of the module file, unifying the code for
searching for a module with a given name (into lookupModule()) and
separating out the mapping to a module file (into
getModuleFileName()). No functionality change.

llvm-svn: 149197

clang/lib/Lex/Preprocessor.cpp

@@ -383,7 +383,7 @@ Module *Preprocessor::getCurrentModule() {
   if (getLangOptions().CurrentModule.empty())
     return 0;
   
-  return getHeaderSearchInfo().getModule(getLangOptions().CurrentModule);
+  return getHeaderSearchInfo().lookupModule(getLangOptions().CurrentModule);
 }
 
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