Fix double menu sound in some cases when entering text

(I don't hear it, but this should fix it.)
Rename fs_file struct to avoid namespace clash in C++ mode
Move several GUI helpers to common code
Add a language selection screen
Add native translations of all language names

Patch by @GunChleoc
Add a dummy en-US language file to force source language
Merge pull request #28 from parasti/language-screen

Language selection screen
Reload resources on language switch to load the localized font
Add WenQuanYi Micro Hei font and switch Traditional Chinese to it
Increase languages per page to fix a 1 language page
Update DejaVu font to v2.34
fs_stdio.c: Match typedef in fs.h
Use _putenv_s on Windows/MinGW
.gitignore the Windows binaries to avoid accidental addition
Update download URLs in install.txt

(Closes #33)
Add command filtering and mute title screen replays

(Closes #6)
Fix Last.nbr being created with the wrong path
Update install.txt

(Closes #32)
Add two sentences on MinGW and Fedora
Explain that ENABLE_NLS is enabled by default