Debugger: More flexibility for "ranged expressions"

The range boundary and stride can be integral expressions.
Also ( ) are valid delimiters now, making descriptions like
list.at(2.(4).100+2) acceptable.

Change-Id: Ief68c0a1b0b0d3813b2939d60e0806f5cd3ff0b0
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@digia.com>