bug#20169: 25.0.50; doc of `posn-actual-col-row'

[Drew Adams]

Please add the information that is in the doc string to (elisp)
`Accessing Mouse'.  This means both the reference information about what
happens if POSITION does not contain the actual position and the guide
information about using `posn-col-row' in that case.

In GNU Emacs 25.0.50.1 (i686-pc-mingw32)
 of 2014-10-20 on LEG570
Bzr revision: 118168 rgm@gnu.org-20141020195941-icp42t8ttcnud09g
Windowing system distributor `Microsoft Corp.', version 6.1.7601
Configured using:
 `configure --enable-checking=yes,glyphs CPPFLAGS=-DGLYPH_DEBUG=1'