Also make sysconf use PTHREAD_STACK_MIN rather than redefining its
own, different, constant.
Bug: 9997352
Change-Id: I9a8e7d2b18e691439abfb45533e82c36eee9e81d
This was originally motivated by noticing that we were setting the
wrong bits for the well-known tls entries. That was a harmless bug
because none of the well-known tls entries has a destructor, but
it's best not to leave land mines lying around.
Also add some missing POSIX constants, a new test, and fix
pthread_key_create's return value when we hit the limit.
Change-Id: Ife26ea2f4b40865308e8410ec803b20bcc3e0ed1
