movfun.m, movslice.m: Add support for even-size, asymmetric windows for Matlab compatibility. * movfun.m: Rewrite documentation about scalar window length WLEN and provide many example usages. Remove input validation check for symmetric window. Remove BIST test checking for error when given an asymmetric WLEN. * movslice.m: Remove input validation check for symmetric window. Detect whether scalar WLEN is even or odd. Add new calculation for indices of asymmetric window. Remove BIST test checking for error when given an asymmetric WLEN.

gnulib = http://hg.octave.org/gnulib