Move ctime() to separate file

localtime() is referenced by do_fstat(), which is always (indirectly)
referenced by the startup code. Having ctime defined in the same file
will also always pull in asctime & strftime.

tz/SRCFILES

@@ -2,6 +2,7 @@
 # the files that should go only into source distributions.
 
 SRCFILES = asctime.c \
+	   ctime.c \
 	   difftime.c \
            localtime.c \
 	   strftime.c \

tz/ctime.c

@@ -0,0 +1,22 @@
+#include "private.h"
+
+/*
+** Section 4.12.3.2 of X3.159-1989 requires that
+**	The ctime function converts the calendar time pointed to by timer
+**	to local time in the form of a string. It is equivalent to
+**		asctime(localtime(timer))
+*/
+char *ctime(const time_t *timep)
+{
+	struct tm *tmp = localtime(timep);
+
+	return tmp ? asctime(tmp) : NULL;
+}
+
+char *ctime_r(const time_t *timep, char *buf)
+{
+	struct tm mytm;
+	struct tm *tmp = localtime_r(timep, &mytm);
+
+	return tmp ? asctime_r(tmp, buf) : NULL;
+}

tz/localtime.c

@@ -1938,27 +1938,6 @@ static struct tm *timesub(const time_t *timep, int_fast32_t offset, struct state
 	return tmp;
 }
 
-/*
-** Section 4.12.3.2 of X3.159-1989 requires that
-**	The ctime function converts the calendar time pointed to by timer
-**	to local time in the form of a string. It is equivalent to
-**		asctime(localtime(timer))
-*/
-char *ctime(const time_t *timep)
-{
-	struct tm *tmp = localtime(timep);
-
-	return tmp ? asctime(tmp) : NULL;
-}
-
-char *ctime_r(const time_t *timep, char *buf)
-{
-	struct tm mytm;
-	struct tm *tmp = localtime_r(timep, &mytm);
-
-	return tmp ? asctime_r(tmp, buf) : NULL;
-}
-
 /*
 ** Adapted from code provided by Robert Elz, who writes:
 **	The "best" way to do mktime I think is based on an idea of Bob