+We assume ANSI C89 plus the following:
+- <stdlib.h>
+- rename()
+- opendir(), readdir(), closedir() (via dirent.h)
+- memchr (via string.h)
+- (a safe) putenv() (via stdlib.h)
+- strtoul() (via stdlib.h)
+(grep for 'define' in uconfig.sh.)
+Also, Perl times() is defined to always return zeroes.