Revise FUSE ABI backwards compatibility

* Introduce inline getters and setters for every FUSE ABI data structue member.

* Reduce overhead when only the newest ABI version is supported, i.e. MacFUSE
  compatibility is disabled.

* It is not ideal to copy too much memory around, therefore we no longer patch
  FUSE ABI data structures before sending or after receiving them but while
  accessing individual members.
Fix warning: unused parameter 'version'
Force inline accessors for FUSE ABI data structure members
Fix CFBundleName of kext bundle