20140603 tpd books/bookvol10.4 fix "bad reduction" in multivariate poly gcd

books/bookvol10.4 fix "bad reduction" in multivariate poly gcd

Add Waldek's patch to PGCD gcd routines. I still don't understand the
algorithm.

src/input/pgcd.input add pgcd test case

Waldek posted this file as the test case. The bug is supposed to be due
to a "bad reduction" in multivariate gcd but the posted test case is
explicitly univariate.

src/input/Makefile add pgcd.input

Add pgcd.input.pamphlet to the automated regression test suite.