Introduce a new lexer function to compute the "preamble" of a file,
which is the part of the file that contains all of the initial
comments, includes, and preprocessor directives that occur before any
of the actual code. Added a new -print-preamble cc1 action that is
only used for testing.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@108913 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/tools/driver/cc1_main.cpp b/tools/driver/cc1_main.cpp
index 841e40a..3b13f0c 100644
--- a/tools/driver/cc1_main.cpp
+++ b/tools/driver/cc1_main.cpp
@@ -102,6 +102,7 @@
   }
 
   case PrintDeclContext:       return new DeclContextPrintAction();
+  case PrintPreamble:          return new PrintPreambleAction();
   case PrintPreprocessedInput: return new PrintPreprocessedAction();
   case RewriteMacros:          return new RewriteMacrosAction();
   case RewriteObjC:            return new RewriteObjCAction();