Fix bug with brackets highlighting
Fix bug with brackets highlighting

In some cases in addition to the pair of brackets are highlighted
extra characters.

For instance, str = "insert into table1(a,b) values (x, y)[caret]";
Left bracket, right bracket, and 'v' symbol are highlighted
(expected brackets only).
Now this bug is fixed: non-brackets symbols aren't highlighted.

fedorovr/YaccConstructor,nbIxMaN/YaccConstructor,nbIxMaN/YaccConstructor,nbIxMaN/YaccConstructor,fedorovr/YaccConstructor,YaccConstructor/YaccConstructor,Albiglittle/YaccConstructor,YaccConstructor/YaccConstructor,YaccConstructor/YaccConstructor,fedorovr/YaccConstructor,Albiglittle/YaccConstructor,Albiglittle/YaccConstructor