* configure.in: Check sys/id.h, getuidx and getgidx for AIX.

* process.c (getresuid): Defined for AIX.
  (getresgid): Ditto
  AIX don't have getresuid/getresgid but getuidx/getgidx.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47397 b2dd03c8-39d4-4d8f-98ff-823fe69b080e