Added special version of string-left-trim for list bag and general string.
Added special version of string-left-trim for list bag and general string.

vtomole/SICL,clasp-developers/SICL,vtomole/SICL,clasp-developers/SICL,vtomole/SICL,clasp-developers/SICL,vtomole/SICL,clasp-developers/SICL