package bzip2: fix runtime crashes

This moves the source modifications from the Makefile into a patch, and it adds
a critical change: instead of removing WINAPI, the whole _WIN32 preprocessor
block is deactivated. This fixes the BZ_API macro.

This is necessary to fix runtime crashes in my application.
Merge pull request #125 from marlam/fix-bzip2

package bzip2: fix runtime crashes