[PATCH 2/3] lib: fix clang build warnings

[Jani Nikula]

Fix the following warning produced by clang 3.5.0:

lib/message.cc:899:4: warning: comparison of constant 64 with expression of type 'notmuch_message_flag_t' (aka '_notmuch_message_flag') is always true [-Wtautological-constant-out-of-range-compare]
        ! NOTMUCH_TEST_BIT (message->lazy_flags, flag))
          ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./lib/notmuch-private.h:70:6: note: expanded from macro 'NOTMUCH_TEST_BIT'
    (_NOTMUCH_VALID_BIT(bit) ? !!((val) & (1ull << (bit))) : 0)
     ^~~~~~~~~~~~~~~~~~~~~~~
./lib/notmuch-private.h:68:26: note: expanded from macro '_NOTMUCH_VALID_BIT'
    ((bit) >= 0 && (bit) < CHAR_BIT * sizeof (unsigned long long))
                   ~~~~~ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
---
 lib/notmuch-private.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/notmuch-private.h b/lib/notmuch-private.h
index 02a8fc62b631..8a1f2fab77af 100644
--- a/lib/notmuch-private.h
+++ b/lib/notmuch-private.h
@@ -65,7 +65,7 @@ NOTMUCH_BEGIN_DECLS
 
 /* Robust bit test/set/reset macros */
 #define _NOTMUCH_VALID_BIT(bit) \
-    ((bit) >= 0 && (bit) < CHAR_BIT * sizeof (unsigned long long))
+    ((bit) >= 0 && ((unsigned long) bit) < CHAR_BIT * sizeof (unsigned long long))
 #define NOTMUCH_TEST_BIT(val, bit) \
     (_NOTMUCH_VALID_BIT(bit) ? !!((val) & (1ull << (bit))) : 0)
 #define NOTMUCH_SET_BIT(valp, bit) \
-- 
2.1.4