Add -Wno-implicit-fallthrough compiler flag for Date

Author: Girgias

ext/date/config0.m4

@@ -4,7 +4,7 @@ AC_CHECK_HEADERS([io.h])
 dnl Check for strtoll, atoll
 AC_CHECK_FUNCS(strtoll atoll)
 
-PHP_DATE_CFLAGS="-I@ext_builddir@/lib -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -DHAVE_TIMELIB_CONFIG_H=1"
+PHP_DATE_CFLAGS="-Wno-implicit-fallthrough -I@ext_builddir@/lib -DZEND_ENABLE_STATIC_TSRMLS_CACHE=1 -DHAVE_TIMELIB_CONFIG_H=1"
 timelib_sources="lib/astro.c lib/dow.c lib/parse_date.c lib/parse_tz.c
                  lib/timelib.c lib/tm2unixtime.c lib/unixtime2tm.c lib/parse_iso_intervals.c lib/interval.c"