added some new tests for old style string format with signed integer decimal
added some new tests for old style string format with signed integer decimal

Hasimir/brython,rubyinhell/brython,kevinmel2000/brython,JohnDenker/brython,rubyinhell/brython,Lh4cKg/brython,olemis/brython,brython-dev/brython,kevinmel2000/brython,molebot/brython,jonathanverner/brython,JohnDenker/brython,kevinmel2000/brython,rubyinhell/brython,Isendir/brython,firmlyjin/brython,molebot/brython,Hasimir/brython,brython-dev/brython,Lh4cKg/brython,Mozhuowen/brython,firmlyjin/brython,Hasimir/brython,firmlyjin/brython,jonathanverner/brython,amrdraz/brython,olemis/brython,jonathanverner/brython,olemis/brython,JohnDenker/brython,Isendir/brython,molebot/brython,Lh4cKg/brython,Isendir/brython,molebot/brython,kikocorreoso/brython,olemis/brython,Hasimir/brython,nvoron23/brython,nvoron23/brython,kevinmel2000/brython,kikocorreoso/brython,amrdraz/brython,brython-dev/brython,nvoron23/brython,Mozhuowen/brython,kikocorreoso/brython,rubyinhell/brython,amrdraz/brython,firmlyjin/brython,Mozhuowen/brython,Lh4cKg/brython,JohnDenker/brython,Mozhuowen/brython,firmlyjin/brython,Isendir/brython,jonathanverner/brython,amrdraz/brython