Fixed libmikmod downloading

For some reason, trying to download this file with `wget --continue` causes an infinite redirect loop, and continuation isn't that useful here anyways, so I disabled that.
Fixed an incorrect invocation breaking SDL_ttf

It's --with-freetype-prefix, not --with-freetype (realized after reading https://github.com/pspdev/psplibraries/issues/14#issuecomment-30774187 and checking what was different from the script)
Fixed pixman
*almost* fixed SDL_gfx
Using psptoolchain's download_and_extract
Merge pull request #19 from uppfinnarn/master

Various fixes