bug#14006: 24.3.50; doc of `completion-in-region-mode', `completion-in-region'

["Drew Adams" <drew.adams@oracle.com>]

Doc string of `completion-in-region-mode' is useless.  It says nothing
more than that the mode is "used during `completion-in-region'.  Used
for what?  Used how?  What does it do?  (And there is a typo presumably:
"modemode".  It doesn't seem like much thought or time was expended on
this doc.
 
Doc string of `completion-in-region' does not say how PREDICATE is used
- what it means to "say when to exit" (how? why? exit what?).  And it
is not clear whether point can be START or END or both or neither:
"between" generally excludes both end points, but the meaning should
be made explicit.  And nothing is said about what COLLECTION is -
"using COLLECTION" means nothing.  At least cross-ref some other doc
that describes COLLECTION.
 
(elisp) `Completion in Buffers' says little more than what the doc
string of `completion-in-region' says.  (At least it cross-references 
COLLECTION.)  And it says nothing about `completion-in-region-mode'.
 
In GNU Emacs 24.3.50.1 (i386-mingw-nt5.1.2600)
 of 2013-03-17 on ODIEONE
Bzr revision: 112068 michael.albinus@gmx.de-20130317173046-sgy1bmmkkizorqby
Windowing system distributor `Microsoft Corp.', version 5.1.2600
Configured using:
 `configure --with-gcc (4.7) --no-opt --enable-checking --cflags
 -IC:/Devel/emacs/build/include --ldflags -LC:/Devel/emacs/build/lib'