Fix highscore entry

- Using SDL text input events everywhere.
- Remove obsolete process method.
More robust tempo handling in midi files.

Added a check to ignore multiple identical tempo changes in a midi
file.
Theoretically, more than one tempo change can not occur at the exact
same time. However, if there are multiple tempo changes at the exact
same time _but with the same target tempo_ there is not really any
reason to bail out.
Merge pull request #101 from gebart/midi-parser-bugfix

More robust tempo handling in midi files.
Fix karaoke key code.
remove exessive semicolons
add some comments to understand how the song scanner works so I can
start building #83
Detect preview.ogg as a preview track and do not use it as BGMUSIC like we did before. Closes bug #96 (I think).
Remove unused variables (Clang warnings).
do some prep work for #83, it doesn't merge the songs yet but at least
it doesn't segfault when scanning, and since it's only in memmory I
discovered it didn't slow down loading that much!
Merge branch 'master' of https://github.com/performous/performous
Merge branch 'master' into webserver