Fix bitmap_sfu() regression.
Fix bitmap_sfu() regression.

Fix bitmap_sfu() to shift by LG_BITMAP_GROUP_NBITS rather than
hard-coded 6 when using linear (non-USE_TREE) bitmap search.  In
practice this affects only 64-bit systems for which sizeof(long) is not
8 (i.e. Windows), since USE_TREE is defined for 32-bit systems.

This regression was caused by b8823ab02607d6f03febd32ac504bb6188c54047
(Use linear scan for small bitmaps).

This resolves #368.

leebaok/jemalloc-4.2.1-readcode,jemalloc/jemalloc-cmake,jemalloc/jemalloc-cmake,glandium/jemalloc,glandium/jemalloc,leebaok/jemalloc-4.2.1-readcode,leebaok/jemalloc-4.2.1-readcode,AndroidExternal/jemalloc,8l/jemalloc,AndroidExternal/jemalloc,jemalloc/jemalloc-cmake,jemalloc/jemalloc-cmake,wqfish/jemalloc,wqfish/jemalloc,8l/jemalloc,wqfish/jemalloc,8l/jemalloc,leebaok/jemalloc-4.2.1-readcode,wqfish/jemalloc,AndroidExternal/jemalloc,wqfish/jemalloc,AndroidExternal/jemalloc,8l/jemalloc,glandium/jemalloc,glandium/jemalloc