Propagating the changes to mcontests (the lack of the silly
is_expr_of_expr) and to mconextract. 

Also removing copied code from mconextract and turning it into
dependence. This requires the extractable reduction to be renamed.
Revert "Propagating the changes to mcontests (the lack of the silly is_expr_of_expr) and to mconextract. "

This reverts commit c15e49e619b650ab7cea5be022802770240381c3.
Propagating the changes to mcontests (the lack of the silly
is_expr_of_expr) and to mconextract. 

Also removing copied code from mconextract and turning it into
dependence. This requires the extractable reduction to be renamed.