Implement some functions needed for cmd.exe to work

[TheNNX]

Proposed changes implement some functions necessary for cmd.exe to start, most notably _getstdfilex, SetStdioPathW (untested/WIP), GetStdioPathW (untested/WIP), WideCharToMultiByte, and change some existing functions (_fileno, FindFirstFile, FindNextFile).

These changes are not sufficient to start cmd.exe. Here is a branch with a quick and dirty hack to get it working, however, better solutions are necessary. Two main problems are:

• Arguments expected by WinCE applications are not passed to the entrypoint by Windows (see issue Windows does not pass arguments to the entrypoint directly #25)
• cmd.exe seems to expect to have a console already allocated (it does some DeviceIoControl calls, which maybe allocate the console - I don't know).

The more serious issue of the two is the first one. I see two main ways to solve it:

• SubsystemTool could patch the PE to add a custom entry point (this is somewhat difficult, as the code section would have to expand)
• Some sort of self modifying code solution - COREDLL could locate the entrypoint like it does in the quick dirty hack, but instead of invoking it, it could stub it out to intercept it. In the intercepting function, COREDLL would repair the entrypoint, and call it with correct arguments.