misc: fixed building alignment issues

fixes #57
building.md: added info about AoEHD now being supported.
add debug overlay grid, togglable with F4
Merge pull request #138 from franciscod/debug_overlay_grid

game: add debug overlay grid, togglable with F4
Add .desktop file and generate placeholder icon.
Merge pull request #81 from boombatower/desktop-file-plus-icon

Add .desktop file and placeholder icon.
Fix warnings on 32 bit systems

- Change format specifiers to not make assumptions about integer and
  size_t sizes
- Change audio hash function to shift a different amount based on
  sizeof(size_t)
Merge pull request #151 from blucoat/32bitfix

misc: fix warnings on 32 bit systems
buildsystem: fixed install path issues from #81
fixed difference