Adding a treatment of complex numbers for the Lindemann-weierstrass t…

…heorem

Main modifications are in ssrnum, ssrint, and algC.  Others are mostly
consequences to make sure it still compiles.

Merge pull request math-comp#119 from maximedenes/econstr

Econstr support

Merge pull request math-comp#119 from maximedenes/econstr

Econstr support

release 1.6

This is a beta release for mathcomp 1.6