Use console output instead of acs.err if the file does not exist after compiling acs with errors
Bump version to 3.1.0

Also update installer script to download and install VS2013 runtimes if needed
ZDoom language configurations update
- DECORATE:
  - Added FPF_AIMATANGLE and FPF_TRANSFERTRANSLATION constants for A_FireCustomMissile.
  - Updated A_FireCustomMissile's syntax to replace 'aim' with 'flags'.
Merge pull request #173 from Blue-Shadow/master

ZDoom language configurations update
Merge branch 'master'