Chez Scheme: fix missing include in externs.h

The correct header is needed to build with musl.

racket/src/ChezScheme/c/expeditor.c

@@ -548,7 +548,6 @@ static void s_ee_write_char(wchar_t c) {
 #endif
 #include <termios.h>
 #include <signal.h>
-#include <time.h>
 #include <fcntl.h>
 #include <sys/ioctl.h>
 #include <wchar.h>

racket/src/ChezScheme/c/externs.h

@@ -23,6 +23,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <errno.h>
+#include <time.h>
 
 #ifndef WIN32
 #include <unistd.h>

racket/src/ChezScheme/c/prim5.c

@@ -21,7 +21,6 @@
 #include <sys/stat.h>
 #include <limits.h>
 #include <ctype.h>
-#include <time.h>
 
 /* locally defined functions */
 static INT s_errno PROTO((void));

racket/src/ChezScheme/c/scheme.c

@@ -20,7 +20,6 @@
 #include <limits.h>
 #ifdef WIN32
 #include <io.h>
-#include <time.h>
 #else
 #include <sys/time.h>
 #endif

racket/src/ChezScheme/c/stats.c

@@ -36,8 +36,6 @@
 #include <sys/resource.h>
 #endif
 
-#include <time.h>
-
 static struct timespec starting_mono_tp;
 
 static long adjust_time_zone(ptr dtvec, struct tm *tmxp, ptr given_tzoff);