Add command to enable writing to const types

[kastiglione]

@rohan-mehta seeded this idea. When a variable is const, lldb will respect that and prevent assignment to the variable. Perhaps we could add a chisel convenience command that does this for the user:

(lldb) e CGFloat *p = (CGFloat *)&constVariable; *p = 1.0

[idrisr]

Is that valid syntax? Am I missing something?

>>>> lldb >>>> e
Enter expressions, then terminate with an empty line to evaluate:
  1: CGFloat *p = (CGFloat *)&constVariable
  2: *p = 1.0
  3:
error: use of undeclared identifier 'constVariable'

[kastiglione]

constVariable refers to the variable that is const, that you want to edit. For example, given this definition:

const CGFloat labelWidth = fullWidth - iconWidth - padding * 2;

If you wanted to reassign labelWidth in lldb, you could use the above statement, except with labelWidth instead of constVariable. Note however, we tried this with x86, but not x86-64, or on arm.