setresuid: generic implementation for all arches

[Arusekk]

Closes #1324

The real uid to set defaults to geteuid() and the remaining uids default to new real uid. Supported usage includes:

• asm(setresuid() + connect(...) + dupsh())
• asm(setresuid(0) + connect(...) + dupsh())
• asm(setresuid(5,6[,5]) + connect(...) + dupsh())
• asm(setresuid(1,2,3) + connect(...) + dupsh())

Hope this proves useful.