Add missing #include, found by modules build.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@237326 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/include/clang/Lex/ExternalPreprocessorSource.h b/include/clang/Lex/ExternalPreprocessorSource.h
index a795a8565d0264066ed9f1a2091e96cc15406387..33e7a2d84b88f7e41d516fcc872d6c516283323b 100644 (file)
--- a/include/clang/Lex/ExternalPreprocessorSource.h
+++ b/include/clang/Lex/ExternalPreprocessorSource.h
@@ -17,6 +17,7 @@
 namespace clang {
 
 class IdentifierInfo;
+class Module;
 
 /// \brief Abstract interface for external sources of preprocessor 
 /// information.