Use right associativity for ternary operator

Author: fvictorio

Solidity.g4

@@ -315,7 +315,7 @@ expression
   | expression ('==' | '!=') expression
   | expression '&&' expression
   | expression '||' expression
-  | expression '?' expression ':' expression
+  | <assoc=right> expression '?' expression ':' expression
   | expression ('=' | '|=' | '^=' | '&=' | '<<=' | '>>=' | '+=' | '-=' | '*=' | '/=' | '%=') expression
   | primaryExpression ;