[RFC] Update version.c to Vim 7.4.444

I updated version.c to Vim 7.4.444 and added some NAs.

NAs list is below.
7.4.413 : GUI problem
7.4.420 : Test documentation problem
7.4.424 : if_python problem
7.4.426 : filelist problem
7.4.428 : Windows issue.  Modified file is nothing.
7.4.431 : Compiler warning
7.4.432 : Windows issue.  Modified file is nothing.
7.4.433 : Windows test issue.

Related issue: https://github.com/neovim/neovim/issues/1147