http: fix undefined-shift in EVUTIL_IS*_ helpers

evutil.c:2559:1: runtime error: left shift of 1 by 31 places cannot be represented in type 'int'
    #0 0x4f2be0 in EVUTIL_ISXDIGIT_ libevent/evutil.c:2559:1
    #1 0x4bd689 in regname_ok libevent/http.c:4838:7
    #2 0x4bc16b in parse_authority libevent/http.c:4958:9
    #3 0x4bb8b5 in evhttp_uri_parse_with_flags libevent/http.c:5103:7
    #4 0x4bb762 in evhttp_uri_parse libevent/http.c:5050:9
    libevent#5 0x4b8f41 in evhttp_parse_query_impl libevent/http.c:3505:9
    libevent#6 0x4b8ed7 in evhttp_parse_query libevent/http.c:3569:9

Bug: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=23291
Report: https://oss-fuzz.com/testcase-detail/5670743106125824
(cherry picked from commit 37dbb35)

Author: azat

evutil.c

@@ -2369,7 +2369,7 @@ static const unsigned char EVUTIL_TOLOWER_TABLE[256] = {
 #define IMPL_CTYPE_FN(name)						\
 	int EVUTIL_##name##_(char c) {					\
 		ev_uint8_t u = c;					\
-		return !!(EVUTIL_##name##_TABLE[(u >> 5) & 7] & (1 << (u & 31))); \
+		return !!(EVUTIL_##name##_TABLE[(u >> 5) & 7] & (1U << (u & 31))); \
 	}
 IMPL_CTYPE_FN(ISALPHA)
 IMPL_CTYPE_FN(ISALNUM)

test/regress_util.c

@@ -984,6 +984,16 @@ test_evutil_rand(void *arg)
 	;
 }
 
+static void
+test_EVUTIL_IS_(void *arg)
+{
+	tt_int_op(EVUTIL_ISDIGIT_('0'), ==, 1);
+	tt_int_op(EVUTIL_ISDIGIT_('a'), ==, 0);
+	tt_int_op(EVUTIL_ISDIGIT_('\xff'), ==, 0);
+end:
+	;
+}
+
 static void
 test_evutil_getaddrinfo(void *arg)
 {
@@ -1611,6 +1621,7 @@ struct testcase_t util_testcases[] = {
 	{ "upcast", test_evutil_upcast, 0, NULL, NULL },
 	{ "integers", test_evutil_integers, 0, NULL, NULL },
 	{ "rand", test_evutil_rand, TT_FORK, NULL, NULL },
+	{ "EVUTIL_IS_", test_EVUTIL_IS_, 0, NULL, NULL },
 	{ "getaddrinfo", test_evutil_getaddrinfo, TT_FORK, NULL, NULL },
 	{ "getaddrinfo_live", test_evutil_getaddrinfo_live, TT_FORK|TT_OFF_BY_DEFAULT, NULL, NULL },
 #ifdef _WIN32