Bugfixes and additional protocol support for extra FIND_FIRST2 functions

These additions queue up support for the SMB functions used by the
ms13_071_theme expoit developed by Juan Vazquez, including support for
the FIND_FIRST2 functions:
 * Find File Both Directory Info
 * Find File Names Info

Additionally this commit fixes a few bugs in how the client SMB payload
is handled to determine whether a file, directory or "not found"
response needs to be returned and allows metasploit to serve arbitrary
files directly over SMB in addition to files being loaded in runtime
processes calling "LoadLibrary".

Author: Matthew Hall