somewhat illogical and temporary workaround to the problems with consolidate & bounce...

somewhat illogical and temporary workaround to the problems with consolidate & bounceable. it turns out that region bouncing never replaces the in-place region, so bounceable() doesn't matter; range bouncing only needs to check bounceable() if we're going to replace material in place and the op is with-processing. reword the error dialog too

git-svn-id: svn://localhost/ardour2/branches/3.0@9606 d708f5d6-7413-0410-9779-e7cbd77b26cf