VERBOSE/verbose and --enable-verbose... (package maintainer may be impacted)

tldr; VERBOSE is not supported anymore, use verbose=t (lowercase) to
get verbose logs. --enable/disable-verbose has been removed from
configure.ac, use verbose=t in your build script instead



Over time VERBOSE/verbose got mangled...
verbose (lowercase) was used to have a 'verbose' output of make,
containing all the command line displayed. that variable was an
empty/non-empty trigger. non-empty => verbose is on

VERBOSE was use as a synonym for verbose.. unfortunatly it also was
used in other place with a YES/NO semantic.
--enable/disable-verbose in configure.ac was followin the YES/NO
semantic with the added twist that if neither was explicitely specify
the varaible stayed empty

so --enable-verbose and --disable-verbose would both be seen as
equivalent to verbose=t

some modules (well canvas and slideshow really) wheres using
VERBOSE=YES/NO to trigger a home-grwon logging mechanism.

I have converted these modules to use SAL_INFO/SAL_WARN instead of the
home grown logging
I have removed the use of VERBOSE in gbuild.. only $(verbose) is honored
I have dropped the --enable-verbose option of configure.ac completely.

these changes have landed in master earlier today.


Norbert