[llvm-rc] Don't strictly require quotes around external file names

Regardless of what docs may say, existing resource files in the
wild can use this syntax.

Rename a file used in an existing test, to make it usable for unquoted
paths.

Differential Revision: https://reviews.llvm.org/D46511

llvm-svn: 331747
diff --git a/llvm/tools/llvm-rc/ResourceScriptParser.h b/llvm/tools/llvm-rc/ResourceScriptParser.h
index e22619a..639ef63 100644
--- a/llvm/tools/llvm-rc/ResourceScriptParser.h
+++ b/llvm/tools/llvm-rc/ResourceScriptParser.h
@@ -84,6 +84,7 @@
   Expected<RCInt> readInt();               // Parse an integer.
   Expected<StringRef> readString();        // Parse a string.
   Expected<StringRef> readIdentifier();    // Parse an identifier.
+  Expected<StringRef> readFilename();      // Parse a filename.
   Expected<IntOrString> readIntOrString(); // Parse an integer or a string.
   Expected<IntOrString> readTypeOrName();  // Parse an integer or an identifier.