Update _SQLGetData - Was incorrectly attempting to validate input of an output only parameter

According to the spec, pcbValue is designated as an output only variable, so there is no need to validate any incoming values.

Some packages do not initialize this variable before passing it into the function call; this will randomly result in an improperly thrown error.

Removed the input validation.
Added missing break in switch/case

That missing break is not just a memory leak:
It results in incorrect call to mdb_unicode2ascii for binary data!
I suspect that is what is causing segfault on some db as repported on
https://github.com/brianb/mdbtools/issues/19
Update _SQLGetData - Was incorrectly attempting to validate input of an output only parameter

According to the spec, pcbValue is designated as an output only variable, so there is no need to validate any incoming values.

Some packages do not initialize this variable before passing it into the function call; this will randomly result in an improperly thrown error.

Removed the input validation.