GCD_Poly_ML: test 2nd level integration of gcd_poly

test --- and app_rev --- shows the respective part of the rewriter

GCD_Poly_ML: correct & improve assumptions generated from gcd_pol

GCD_Poly_ML: test 1st level integration of gcd_poly

tuned

GCD_Poly_ML: integrated gcd_poly into Rational.thy

replaced exactly fun factout_p_, fun cancel_p_, fun common_nominator_p_, fun add_fraction_p_
and left the other old code in the file in order to find out further functions still required.
Test_Isac.thy works except "exception- Size raised" in solve.sml,
polyeq.sml is out commented (but works if evaluated in two pieces).

Test_Isac doesn't work anymore

after successful build of session Isac
./bin/isabelle jedit -l Isac test/Tools/isac/Test_Isac.thy &
# launches jEdit
# loads the required theories
# once highlights the additional theories required
# and then doesn't start evaluation with 10 minutes.

next trial will delete the old Unsynchronized.ref in Rational.thy
which are not necessary anymore.

GCD_Poly_ML: deleted unused code for cancellation and add.of.fract

this code concerned a format of polynomials which turned out uneasy in 2003

GCD_Poly_ML: integrated tests, reactivated test/../rational.sml

GCD_Poly_ML: conversions term <--> poly

not contained in GCD_Poly_ML, because the latter is meant for TUM,
while conversions use lots of Isac tools.

GCD_Poly_ML: minimise negative coefficients