fix: mod_ now indep. of implementation details of mod
temporary disable Short/parallel_s.tst as it leaves Singular processes running
fixing bug (use of non-initialized value) in nlClearDenominators and minor improvements
chg: mod/div for bigint
fix: nlClearDenominator: less nlNormalize, positive leadcoeff
fix: div/mod stuff for paraPlanCurve: aDiv, aMod
chg: IntDiv/IntMod postponed
fix: nlClearDenom/nlContent: lead coeff >0
fix: nlContent
fix: memory leak in walk
add: extgcd for bigint
fix: npInit for large ints
correcting polymake.lib inclusion
warnings elimination

chg: uninitialized fake variables
chg: "'const' type qualifier on return type has no effect" for numeric/
chg: more minor warnings elimination
fixed a bug in naInvers for the case of non-irreducible minpoly and division by a zero-divisor
fix: bb used as function (tr #445)
fix: enterpairsSpecial for HAVE_RINGS
fix: spielwiese patch
chg: moved some link stuff to links/*
Make debuging objects (_g) a configure option.