Remove unfinished NEON version of vectorized rotate sampling

A vectorized codepath for rotating transforms were added in 5.3.0, but
was only properly tested for SSE2. The NEON version remains unfinished.
Since it was never working, this patch reverts the NEON version.

Task-number: QTBUG-39445
Change-Id: Ifbce0e03781d217ad976c6b18ac88381055cba66
Reviewed-by: Gunnar Sletta <gunnar.sletta@jollamobile.com>
Ensure that there is no duplication of the output directory in output

When a relative path was specified as the output then it would be in both
Option::output_dir and Option::output. Therefore in that case
Option::output should be just the filename as Option::output_dir has the
correct path to output to.

Task-number: QTBUG-39460
Change-Id: Idc988e6bad94f34b89660fb5e8d6fa3a39dc623b
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>