* arts-2-1-626

* src/matpack*.h (*::get):

Add a non-asserting element accessor to Vector, Matrix and Tensor*
View classes. Should only in places were maximum speed is of the essence.

* src/interpolation.{h,cc}:

Cache the begin() and end() iterators in loops. Use the matpack get
function inside the loops.

Speeds up interpolation, especially the GasAbsLookup::Extract function.
For example, arts.ctlfile.slow.amsub runs 30% faster.

* src/m_rte.cc (yCalc), src/rte.cc (iyb_calc):

Tweak OpenMP loop condition for cases where the number of frequencies
is smaller than nmblock and nza.

git-svn-id: https://www.sat.ltu.se/svn/rt/arts/trunk@8407 aaf1aab0-4228-0410-ad68-8dceda47f409