symfun: numel=1, size=(1,1), helps with matlab and also matches SMT

SMT does this.  This nicely works around lots of instances of #107 too.
Perhaps leave open for now.

Fixes #109.
symfun/size  to (1,1)
matlab: assert needs logical input
workaround strange bug on Matlab 2014a

See issue #111.
Merge pull request #112 from cbm755/symfun_numel

Symfun numel