Fix <time.h> check

We're conditionally including based on HAVE_TIME_H in a bunch of places,
but we're not actually checking for time.h, so that's never going to be defined.

While at it, add in a missing include in the cram plugin.

This fixes a bunch of implicit declaration warnings:
```
 * cyrus-sasl-2.1.28/lib/saslutil.c:280:3: warning: implicit declaration of function ‘time’ [-Wimplicit-function-declaration]
 * cyrus-sasl-2.1.28/lib/saslutil.c:364:41: warning: implicit declaration of function ‘clock’ [-Wimplicit-function-declaration]
 * cyrus-sasl-2.1.28/plugins/cram.c:132:7: warning: implicit declaration of function ‘time’ [-Wimplicit-function-declaration]
 * cyrus-sasl-2.1.28/lib/saslutil.c:280:3: warning: implicit declaration of function ‘time’ [-Wimplicit-function-declaration]
 * cyrus-sasl-2.1.28/lib/saslutil.c:364:41: warning: implicit declaration of function ‘clock’ [-Wimplicit-function-declaration]
 * cyrus-sasl-2.1.28/plugins/cram.c:132:7: warning: implicit declaration of function ‘time’ [-Wimplicit-function-declaration]
```

Signed-off-by: Sam James <sam@gentoo.org>

configure.ac

@@ -1290,7 +1290,7 @@ AC_CHECK_HEADERS_ONCE([sys/time.h])
 
 AC_HEADER_DIRENT
 AC_HEADER_SYS_WAIT
-AC_CHECK_HEADERS(crypt.h des.h dlfcn.h fcntl.h limits.h malloc.h paths.h strings.h sys/file.h sys/time.h syslog.h unistd.h inttypes.h sys/uio.h sys/param.h sysexits.h stdarg.h varargs.h krb5.h)
+AC_CHECK_HEADERS(crypt.h des.h dlfcn.h fcntl.h limits.h malloc.h paths.h strings.h sys/file.h sys/time.h syslog.h time.h unistd.h inttypes.h sys/uio.h sys/param.h sysexits.h stdarg.h varargs.h krb5.h)
 
 IPv6_CHECK_SS_FAMILY()
 IPv6_CHECK_SA_LEN()

plugins/cram.c

@@ -53,6 +53,10 @@
 #endif
 #include <fcntl.h>
 
+#ifdef HAVE_TIME_H
+#include <time.h>
+#endif
+
 #include <sasl.h>
 #include <saslplug.h>
 #include <saslutil.h>