Extend C to ignore Visual Studio artifacts

Visual Studio creates a few artifacts which weren't ignored before,
mainly .idb, .pdb and .ilk files which are either created by CL.EXE or
by LINK.EXE were added to the gitignore for Windows projects.

A little more information can be found here on Microsoft's
documentation: https://msdn.microsoft.com/en-us/library/3awe4781.aspx