r17569: Make 'max smbd processes' more robust. Counting on the child to decrement a

r17569: Make 'max smbd processes' more robust. Counting on the child to decrement a
tdb entry is not the most reliable way to count children correctly.

This increments the number of children after a fork and decrements it upon
SIGCLD. I'm keeping a list of children just for consistency checks, so that we
at least get a debug level 0 message if something goes wrong.

Volker
(This used to be commit eb45de167d24d07a218307ec5a48c0029ec097c6)