required by the C standard when called with an invalid base:
strtoll(), strtoimax(), strtoul(), strtoull(), and strtoumax().
Same behaviour for strtoq() and strtouq() even though not standardized.
No functional change in strtol(), it was the only one already correct.
While here, simplify the conditional expression for checking the base
and sync whitespace and comments among the six files.
ok millert@