Fix build under gcc.

Patch from Dawn.


git-svn-id: https://llvm.org/svn/llvm-project/llvdb/trunk@142402 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/source/Host/common/FileSpec.cpp b/source/Host/common/FileSpec.cpp
index 35e12eb..b6e6e94 100644
--- a/source/Host/common/FileSpec.cpp
+++ b/source/Host/common/FileSpec.cpp
@@ -711,7 +711,7 @@
     if (filename == NULL)
         return ConstString();
     
-    char* dot_pos = strrchr(filename, '.');
+    const char* dot_pos = strrchr(filename, '.');
     if (dot_pos == NULL)
         return ConstString();
     
@@ -725,7 +725,7 @@
     if (filename == NULL)
         return ConstString();
     
-    char* dot_pos = strrchr(filename, '.');
+    const char* dot_pos = strrchr(filename, '.');
     if (dot_pos == NULL)
         return m_filename;