Write llvm-tblgen backends as functions instead of sub-classes.

The TableGenBackend base class doesn't do much, and will be removed
completely soon.

Patch by Sean Silva!

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158311 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/TableGen/TableGenBackend.cpp b/lib/TableGen/TableGenBackend.cpp
index 09bcc7a..8117250 100644
--- a/lib/TableGen/TableGenBackend.cpp
+++ b/lib/TableGen/TableGenBackend.cpp
@@ -19,9 +19,12 @@
 
 void TableGenBackend::EmitSourceFileHeader(StringRef Desc,
                                            raw_ostream &OS) const {
+  emitSourceFileHeader(Desc, OS);
+}
+
+void llvm::emitSourceFileHeader(StringRef Desc, raw_ostream &OS) {
   OS << "//===- TableGen'erated file -------------------------------------*-"
        " C++ -*-===//\n//\n// " << Desc << "\n//\n// Automatically generate"
        "d file, do not edit!\n//\n//===------------------------------------"
        "----------------------------------===//\n\n";
 }
-