libc: add function of pgid for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add getpgrp for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add getppid for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add getpwnam_r to porting CRuby

getpwnam_r and getpwuid_r is almost same function.
So, implement getpw_r for commonly function and
To change the two function to call getpw_r

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add setegid for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add seteuid for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add setregid for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add setreuid for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add sid function for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
libc: add waitpid for porting CRuby

Signed-off-by: KANATSU Minoru <icc.pot.tyew272@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>