Hard-coding of the kext installation path now uses KERNEL_MODPREFIX (exported through zfs_config.h). Some small cleanups.
Stricter checking. zfs.kext is loaded from the path specified in KERNEL_MODPREFIX but not if another zfs.kext also exists in /System/Library/Extensions
Merge pull request #136 from RJVB/master

modifications to the zfs.kext loading code