Merge branch 'feature/kostyantyn/buildopt' into 'master'

Boost build time of E-ACSL dependencies

This merge requests addresses issue #23 and suggests the following changes:

- Adopt portable implementation of gmp (called mini-gmp). 
- Switch between full GMP library and mini-gmp library via --enable-full-gmp option in configure. By default mini-gmp is chosen. 
- Reduce the size of GMP distribution shipped with E-ACSL


See merge request !72