Change of dimensions and permutations of linear expressions of level 1

Function: bool ap_linexpr1_extend_environment (ap_linexpr1_t* nexpr, ap_linexpr1_t* expr, ap_environment_t* nenv)

Function: bool ap_linexpr1_extend_environment_with (ap_linexpr1_t* expr, ap_environment_t* nenv)

Change the current environment of the expression expr with a super-environment nenv. Return true if nenv is not a superenvironment.

The first version store the result in the uninitialized *nexpr, the second one updates in-place its argument.