MFC r295856 (by des@):

MFC r295856 (by des@):
Implement /proc/$$/limits.

MFC r297781 (by dchagin@):
More complete implementation of /proc/self/limits.
Fix the way the code accesses process limits struct - pointed out by mjg@.

MFC r298318, 298319 (by cem@):
Don't print uninitialized values and initialize error return before use.

PR:		207386

git-svn-id: svn://svn.freebsd.org/base/stable/10@299221 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f