Fixed a bug and use flint's div_series.
Fixed some bugs and added some generic divexacts.
Added specialised divexact for polys over QQ.
Fixed more fmpq &(x.data) problems.
Merge remote-tracking branch 'wbhart/master'
Fixed == for power series.
Fixed a needs_parentheses bug.
Merge remote-tracking branch 'fredrik/master'
Merge remote-tracking branch 'wbhart/master'
use divexact instead of /