Following up on r1534102, remove special include for psapi function
definitions.

* subversion/libsvn_subr/sysinfo.c
  (includes): Remove several windows specific includes and rely on apr.h
    to do the right thing.

Suggested by: ivan


git-svn-id: https://svn.apache.org/repos/asf/subversion/trunk@1534181 13f79535-47bb-0310-9956-ffa450edef68