fix: includes for SINGULAR_4_1
fix: memory leak: assign list-elem to newstruct
Hiding all the implementation details (or adding the counting & extern declaration) mostly by
moving internal declarations from private headers into corresponding source files

rm: Remove internal includes (hiding privates) + cleanup
chg: cleanup internal headers
fix the usage of internal implementation functions of coeffs from outside of libpolys/coeffs (or libpolys/polys/ext_fiels)
fix header includes for coeffs/AE*.{h,cc}

also starting to fix bigint handling
Fix including "libpolys/" and removal of unnecessary header includes + minor cleanup
Fix slimgb (tgb*) to count the use of inline 'np[A-Z][a-z]*M' functions from modulop.h

CHG: internal (non-inline) np[A-Z][a-z]* calls replaced by corresponding inline wrapper n_[A-Z][a-z]*
Removed the definition of convFactoryNSingAN from clapconv.cc in favor of using n_convFactoryNSingN (=nlConvFactoryNSingN in this case)
Mark deprecated BIGINT handling + related bugs / side effects

FIXMEs: nlGMP -> n_MPZ. Check for side effects and nlMapGMP
Fix: bug in BIGINT deletion
Fix: a possible bug due to sideeffect!?
FIX: Include misc/aux before testing for SINGULAR_4_1
Note that n_CoeffRingQuot1 should replace numbercoeffs