Did you run the "configure" program first (via "sh ./configure" or
equivalent)? Without doing this, things such as strtoul or strerror are
sometimes mentioned as missing.
Tcl includes equivalents for at least the following functions and
include files which may not be found on some systems:
dirent.h limits.h stdlib.h string.h opendir.c
strerror.c strstr.c strtol.c strtoul.c strtod.c