add 'concat! : List % -> %' in URAGG
Remove 'Reference' for Domain local variables
Move implementation of 'first(x, n)' from STAGG to URAGG; specialize in List
Move implementation of '#' under condition in URAGG
Speed up polynomial evaluation
Add own implementation of 'atan' and 'atanh'
Avoid unsound use of Complex
Fix gcd in Factored
minor documentation fixes
Fix a thinko