Merge branch 'nd/threaded-index-pack'

Enables threading in index-pack to resolve base data in parallel. By Nguyễn Thái Ngọc Duy (3) and Ramsay Jones (1) * nd/threaded-index-pack: index-pack: disable threading if NO_PREAD is defined index-pack: support multithreaded delta resolving index-pack: restructure pack processing into three main functions compat/win32/pthread.h: Add an pthread_key_delete() implementation