fix: segfault in > 2 Variable case
chg: use primitive psr gcd
chg: make modular resultant public
chg: use modular resultant in alg_factor
chg: use factory factorization in alg_factor
chg: added function to determine multiplicity of factors
chg: added two new psqr functions
chg: added QuasiInverse over alg. function field
chg: added evaluation function that keeps poly integral
fix: simpleextension
fix: handling of SW_RATIONAL in myfitting
chg: added 'subst' to substitute alg. variables in f by their
 image in the absolute extension
chg: separate non function field case from function field case
chg: better readability of code
chg: remove first factor only if it's constant
chg: do not switch on SW_RATIONAL
chg: make f quasi monic
chg: use factory's factorization
chg: better recovery of factors
chg: compute back substitutions
chg: improve QuasiInverse