[clang-tidy] Test username substitution in TODO() check.

Summary:
This patch depends on D5501.
Check user name substitution more specifically by specifying it via the new
-config= option.
This also lets clang-tidy tests specify clang-tidy options before the '--'
when using check_clang_tidy_fix.sh.

Reviewers: klimek

Reviewed By: klimek

Subscribers: curdeius, cfe-commits

Differential Revision: http://reviews.llvm.org/D5502

llvm-svn: 218515
diff --git a/clang-tools-extra/test/clang-tidy/avoid-c-style-casts.c b/clang-tools-extra/test/clang-tidy/avoid-c-style-casts.c
index 2bdad17..87d1dfc 100644
--- a/clang-tools-extra/test/clang-tidy/avoid-c-style-casts.c
+++ b/clang-tools-extra/test/clang-tidy/avoid-c-style-casts.c
@@ -1,4 +1,4 @@
-// RUN: $(dirname %s)/check_clang_tidy_fix.sh %s google-readability-casting %t -x c
+// RUN: $(dirname %s)/check_clang_tidy_fix.sh %s google-readability-casting %t -- -x c
 // REQUIRES: shell
 
 void f(const char *cpc) {