patch 8.1.2326: cannot parse a date/time string

Problem:    Cannot parse a date/time string.
Solution:   Add strptime(). (Stephen Wall, closes #)
diff --git a/src/configure.ac b/src/configure.ac
index 4065817..6a10638 100644
--- a/src/configure.ac
+++ b/src/configure.ac
@@ -3744,8 +3744,8 @@
 	memset mkdtemp nanosleep opendir putenv qsort readlink select setenv \
 	getpgid setpgid setsid sigaltstack sigstack sigset sigsetjmp sigaction \
 	sigprocmask sigvec strcasecmp strerror strftime stricmp strncasecmp \
-	strnicmp strpbrk strtol tgetent towlower towupper iswupper tzset \
-	usleep utime utimes mblen ftruncate unsetenv posix_openpt)
+	strnicmp strpbrk strptime strtol tgetent towlower towupper iswupper \
+	tzset usleep utime utimes mblen ftruncate unsetenv posix_openpt)
 AC_FUNC_SELECT_ARGTYPES
 AC_FUNC_FSEEKO