Implement getpwnam_r(3) and getpwuid_r(3).

These functions were already declared in <pwd.h>, but hadn't been implemented
yet.

git cherry-pick --no-commit 081504af74826bad7035669ad34d457b4b439e8f

Change-Id: I316acf4cffb9f2c6788e8e342aa620f9a00886d5
1 file changed