Fix parsing of unary expressions.

Fix parsing of unary expressions.

Prohibit the lexer to synthesize a semicolon token after the
colon-sign of a binding declaration.

The parser internally was rewriting the following bindings

   Component.onCompleted:
   ++foo

as

   Component.onCompleted: ;
   ++foo

Task-number: QTBUG-21310
Change-Id: I0558d17fd81b5abac81fb990502d49767ea40730
Reviewed-by: Christian Kamm <christian.d.kamm@nokia.com>
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>