.gitignore stuff

The following changes have been made to .gitignore files in the objs/ and bin/ folders:

• All the .gitignores living in subfolders of objs/ have been done away with and replaced with a single objs/.gitignore, covering all the things that the subfolders ignored before (including depend.ped, if anyone is like me and has to remove that file manually)
• All the .gitignores living in subfolders of bin/Mingw ignore .exes of any name, not just srb2win/srb2dd/srb2sdl. en.mo is also ignored now... or rather any .mo file (just in case). This is mostly for my own sanity and that of anyone else who uses EXENAME=[name.exe] when compiling with MinGW.

If you're not sure what .gitignore does exactly, as far as I'm aware it literally just tells Git what to "ignore" (or rather, not track), so anyone using Git GUI or some other Git program etc doesn't have to see changes certain files and can't accidentally commit the files or whatever.