Named FastFeatureDetector::Type to allow its use in makePtr.

It has actually worked before (likely because it's inside a class),
but C++03 does disallow unnamed types as template arguments,
and there's a report that at least in one version of GCC it's
enforced: <http://code.opencv.org/issues/3278>.
Revert "Fixed a bug in FLANN resulting in uninitialized accesses."

This reverts commit a9975b144a22e76228125eb0a25f78ec13db6815, to prepare
for cherry-picking upstream's solution.
Cherry-picked mariusmuja/flann@b615f2694723fe402b8bbe50d77e622beff7f171.

Original author: Alex Wilson.
Cherry-picked mariusmuja/flann@8c8b0e0cb879666797ab2ac51b9ee438bf84a183.

Original author: me.
Merge pull request #1550 from SpecLad:flann-uninit-master
Merge pull request #1543 from SpecLad:name-enum