std: fix linux uid_t, use uid_t/gid_t in std.os

- correct uid_t from i32 to u32 on linux
- define uid_t and gid_t for OSes missing definitions
- use uid_t/gid_t instead of plain u32s throughout std.os
e8a2aecd2fIsaac Freund committed on 9/3/2020, 1:08:37 PMparent2614067
9 files changedLine totals unavailable