fix: more bigint instead of number
fix: qsort_r

qsort_r is non-standard, esp. BSD and (newer) LINUX define it differently.
At least one has to test for it (testing OS is not enough).
chg: old comments -> doxygen
chg: more old comments -> doxygen
chg: more docu changes
chg: more consistent nomenclature
fix some wrong latex
chg: docu of NTLconvert -> doxygen
chg: better docu for absFactorize