configure: check for pthread_attr_setinheritsched()

Rely on default thread inheritance when not found.
configure: check for endgrent()
platform: work around missing symbol guard

Issue #17
Merge pull request #18 from kodabb/android2

Further android fixes
prep for release
libstc++ mingw threading broken in recent gcc's
mingw fixups
more mingw gcc pthread integration, seems to work
Merge branch 'master' of tycho:sources/ucommon
more mingw cleanup
updated changelog for release