Fix comment in Windows Makefile.

Backport of r1462738 from trunk
resp. r1462739 from 1.5.x resp.
r1462740 from 1.4.x resp.
r1462741 from 1.3.x.


git-svn-id: https://svn.apache.org/repos/asf/apr/apr/branches/1.2.x@1462742 13f79535-47bb-0310-9956-ffa450edef68