[ASan] Split ASan interface header into private and public parts. Add a test that makes sure users can include interface header

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@174058 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/asan/asan_internal.h b/lib/asan/asan_internal.h
index 5d3bffa..dfab3f0 100644
--- a/lib/asan/asan_internal.h
+++ b/lib/asan/asan_internal.h
@@ -15,6 +15,7 @@
 #define ASAN_INTERNAL_H
 
 #include "asan_flags.h"
+#include "asan_interface_internal.h"
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_internal_defs.h"
 #include "sanitizer_common/sanitizer_stacktrace.h"