nixpkgs: remove pthreadmanpages
nixpkgs: remove pthreadmanpages

pthreadmanpages was removed in 9aa1cb6c59f7afc93d72037ab4477d5c259a3ff8
upstream (nixpkgs repository). That commit states:

    pthread-man-pages: Remove

    As far as I can tell, the man-pages package provides documentation for
    every function provided by pthread-man-pages except
    pthread_mutexattr_setkind_np, which no longer appears in the Glibc
    headers. So let's ditch it.

listx/syscfg,listx/syscfg,listx/syscfg,listx/syscfg,listx/syscfg