MAINT: Simplify scalar power
MAINT: Simplify scalar power

This consolidates the multiple copies of almost identical scalar power
code. It fixes the insignificant fact, that integers were doing some
floating point flag handling, even though our scalar power does not
use that.
The previous code special cased powers of 0, but the C-function seems
to handle it just fine.

charris/numpy,mhvk/numpy,pbrod/numpy,numpy/numpy,madphysicist/numpy,charris/numpy,pbrod/numpy,seberg/numpy,madphysicist/numpy,numpy/numpy,madphysicist/numpy,jakirkham/numpy,mattip/numpy,jakirkham/numpy,seberg/numpy,grlee77/numpy,mhvk/numpy,seberg/numpy,endolith/numpy,mhvk/numpy,pbrod/numpy,pdebuyl/numpy,simongibbons/numpy,pdebuyl/numpy,pbrod/numpy,anntzer/numpy,anntzer/numpy,grlee77/numpy,madphysicist/numpy,endolith/numpy,simongibbons/numpy,rgommers/numpy,charris/numpy,simongibbons/numpy,rgommers/numpy,anntzer/numpy,simongibbons/numpy,mattip/numpy,mhvk/numpy,jakirkham/numpy,grlee77/numpy,anntzer/numpy,madphysicist/numpy,endolith/numpy,simongibbons/numpy,jakirkham/numpy,pbrod/numpy,endolith/numpy,grlee77/numpy,numpy/numpy,mattip/numpy,jakirkham/numpy,numpy/numpy,rgommers/numpy,pdebuyl/numpy,rgommers/numpy,pdebuyl/numpy,mattip/numpy,mhvk/numpy,grlee77/numpy,charris/numpy,seberg/numpy