r24496: Add initial synonym handling to "net conf":

r24496: Add initial synonym handling to "net conf":
When storing parameters in the smbconf portion of the registry,
up to now, synonyms could be misused to store a parameter twice.
Now this is prevented by canonicalizing the paramter name first.

Also, the value for a boolean parameter checked for validity
before storing the bool in registry.

(The canonicalization should finally go into the registry smbconf
code to also prevent e.g. "regedit" or "net rpc registry" from
storing synonyms. - This is in the making.)

Michael
(This used to be commit 95447dde860f54d835b3fe90d95fe60231788d1b)