Returning ESRCH for invalid pthread_t

[Bruce Cran]

Hi,

I've been working on standards/125751: after talking to jilles@ I've
decided that we shouldn't change pthread_getschedparam since its
behaviour isn't specified by POSIX. However I'd like to get feedback
about the change to make thread search functions return ESRCH instead of
EINVAL even when a totally bogus id is given, since I'm not very
familiar with either POSIX or pthreads.

-- 
Bruce Cran