pager: set LV=-c alongside LESS=FRSX

On systems with lv configured as the preferred pager (i.e.,
DEFAULT_PAGER=lv at build time, or PAGER=lv exported in the
environment) git commands that use color show control codes instead of
color in the pager:

	$ git diff
	^[[1mdiff --git a/.mailfilter b/.mailfilter^[[m
	^[[1mindex aa4f0b2..17e113e 100644^[[m
	^[[1m--- a/.mailfilter^[[m
	^[[1m+++ b/.mailfilter^[[m
	^[[36m@@ -1,11 +1,58 @@^[[m

"less" avoids this problem because git uses the LESS environment
variable to pass the -R option ('output ANSI color escapes in raw
form') by default.  Use the LV environment variable to pass 'lv' the
-c option ('allow ANSI escape sequences for text decoration / color')
to fix it for lv, too.

Noticed when the default value for color.ui flipped to 'auto' in
v1.8.4-rc0~36^2~1 (2013-06-10).

Reported-by: Olaf Meeuwissen <olaf.meeuwissen@avasys.jp>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -567,6 +567,10 @@ be passed to the shell by Git, which will translate the final
 command to `LESS=FRSX less -+S`. The environment tells the command
 to set the `S` option to chop long lines but the command line
 resets it to the default to fold long lines.
++
+Likewise, when the `LV` environment variable is unset, Git sets it
+to `-c`.  You can override this setting by exporting `LV` with
+another value or setting `core.pager` to `lv +c`.
 
 core.whitespace::
 	A comma separated list of common whitespace problems to