`cygwin_set_impersonation_token'.
* dcrt0.cc (dll_crt0_1): Eliminate superfluous conditional
statements.
Add load statements for `ImpersonateLoggedOnUser', `LogonUserA'
and `RevertToSelf'.
* fork.cc (fork): Care for correct impersonation of parent
and child process.
* security.cc (cygwin_set_impersonation_token): New function.
(cygwin_logon_user): Ditto.
shared.h (class pinfo): New members `orig_uid', `orig_gid',
`real_uid' nad `real_gid'.
spawn.cc (spawn_guts): Care for impersonation when starting
child process in a different user context.
* syscalls.cc (setgid): Call `setegid' now. Set real_gid.
(setuid): Call `seteuid' now. Set real_uid.
(seteuid): Functionality moved from setuid to here. Care for
correct impersonation.
(setegid): Functionality moved from setgid to here.
* uinfo.cc (uinfo_init): Initialization of additional pinfo
members.
(getuid): Return real uid.
(getgid): Return real gid.
(geteuid): Return effective uid.
(getegid): Return effective gid.
include/sys/cygwin.h: Add prototypes for `cygwin_logon_user' and
`cygwin_set_impersonation_token'.
include/cygwin/version.h: Bumb API minor version to 22.
* external.cc: Eliminate obsolete include.
* getopt.c (getopt_long): Fix compiler warning.
* shared.h: Moved PID_ definitions to include/sys/cygwin so that they can be
used by external programs.
* include/sys/cygwin.h: Move external definitions here. Include sys/resource.h
to avoid having to do this everywhere.
