some const char * trivia

[Andrew Cagney]

I got slightly carried away with trying to eliminate some 
-Wwrite-strings errors.  I'm trying to put the resultant mess on 
cagney_writestrings-20030508-branch.  Anyway, I learnt two things:

- the cli callbacks cause much grief
An incremental approach where a new call back function signature (that 
took a const char *) was introduced might make that transition easier.

- strtol(const char *, char **, int base) is a pain
Perhaphs something like:
LONGEST strtolongest (const char *b, const char **p, int base);
would be useful.

Andrew