added some tests for old string formatting of signed integer decimal
added some tests for old string formatting of signed integer decimal

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