K&R calma: remove system header time() K&R style prototype

time.h has existed since C89 so is a standard header expected
to always be available.

sys/time.h was an optional header that historically only some
platforms provided.

If there is a conflict on specific platforms it is better to
'#if !defined()' that specific niche platform with the problem
if both headers are included in the same compile unit.  But I
don't think this is a problem in modern times.

So this results in a resolution that removes #ifdef around
time.h and the detection by configure for the availabiltiy
of sys/time.h.

K&R obsolete syntax removal for C23 compatibility series

calma/CalmaWrite.c

@@ -28,9 +28,8 @@ static char rcsid[] __attribute__ ((unused)) ="$Header: /usr/cvsroot/magic-8.0/c
 #include <ctype.h>
 #include <sys/types.h>
 #include <arpa/inet.h>	/* for htons() */
-#if defined(SYSV) || defined(EMSCRIPTEN)
-#include <time.h>
-#else
+#include <time.h>       /* since C89 */
+#ifdef HAVE_SYS_TIME_H
 #include <sys/time.h>
 #endif
 
@@ -164,9 +163,6 @@ HashTable calmaLibHash;
 HashTable calmaPrefixHash;
 HashTable calmaUndefHash;
 
-/* Imports */
-extern time_t time();
-
 
 /* -------------------------------------------------------------------- */
 

scripts/configure.in

@@ -150,6 +150,9 @@ AC_CHECK_HEADERS(param.h)
 dnl Check for <paths.h>
 AC_CHECK_HEADERS(paths.h)
 
+dnl Check for <sys/time.h>
+AC_CHECK_HEADERS(sys/time.h)
+
 dnl Check for va_copy
 AC_CACHE_CHECK([for va_copy], ac_cv_c_va_copy,
  AC_TRY_LINK(