Build of the branch local-set-param with "long double"

This binaries where compiled with the experimental WITH_LONG_DOUBLE defined, that means it's using "long double" instead of "double" for the solver (GMPL remain using doubles), in my tests as it is now it's around 2 times slower than using "doubles" and for some problems it shows a different solution, it probably can benefit from tunning several constants in src/glpk_real.h