Revert "Do not install extension modules into sys.path"

This reverts commit 3ca5aed602d8fdef6227e329de8272719663bc9a.
Revert "Load extensions from PIL package"

This reverts commit dd80ba22cd3fada2ed0808feea59be6fe911e2a0.
Revert "Use relative import for _imaging"

This reverts commit aff6eccec521fbdfd3e76d593a2d04cd920d1c40.
Revert "Use relative import for _imagingmath"

This reverts commit c731513318c6260bca08569c0197ddf8f4e61967.
Revert "Use relative import for _imagingcms"

This reverts commit 1003e4f7ee4f708045d671837fcfd6d0d4d80373.
Revert "Better import for _imagingft"

This reverts commit 089a04bce1dd3e4de84ef1e7020326339fd3a863.
Revert "Use relative import for _imaginggl"

This reverts commit 5e203de32710b9bac0f0d6870e4e77f78f99c782.
Revert "Use relative import for _imagingtk"

This reverts commit 5820716eb315d1085a2f3900b70ef332b32a6789.
Revert "Use relative import for _imagingagg"

This reverts commit 34a5311e1b6ecd03322bf82ab7972c4aedf43ba9.