Clarified message when nothing to merge is seen. Sometimes there's a non-tip head waiting to be merged, especially after pulling in remote changes while there were local modifications in the working directory which had to be committed before 'hg merge' can work.

%% no changes
%% no changes
%% uncompressed contents in repo
this is a test
%% uncompress our working dir copy
this is a test
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
%% uncompress our new working dir copy
this is a test