Rename set_perms_saved_uid() -> set_perms_posix()
Make set_perms_setreuid simply be set_perms_fallback() and simply include
the appropriate function at compile time (setreuid() vs. setuid()).
o stay_setuid - sudo will remain setuid if system has saved uids or setreuid(2)
o env_reset - reset the environment to a sane default
o env_keep - preserve environment variables that would otherwise be cleared
No longer use getenv/putenv/setenv functions--do environment munging by hand.
Potentially dangerous environment variables can be cleared only if they
contain '/' pr '%' characters to protect buggy programs.
Moved environment routines into env.c (new file)
if available.
Added stay_setuid option for systems that have libraries that perform
extra paranoia checks in system libraries for setuid programs (ie:
anything with issetugid(2)).
