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".