schlock global variable needs to be volatile

Reviewed-by: NAndy Polyakov <appro@openssl.org>
Reviewed-by: NRich Salz <rsalz@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/4000)

apps/speed.c

@@ -275,7 +275,8 @@ static SIGRETTYPE sig_done(int sig)
 # if !defined(SIGALRM)
 #  define SIGALRM
 # endif
-static unsigned int lapse, schlock;
+static unsigned int lapse;
+static volatile unsigned int schlock;
 static void alarm_win32(unsigned int secs)
 {
     lapse = secs * 1000;