* examinememory: evaluate addr as expression
This makes it easy to read memory locations at an offset of a known
address, e.g.:
x 0xc000046800 + 32
* use feedback from @aarzilli
- expression mode is now enabled via -x flag
- support "-x var", "-x &var" in addition to "-x <addr expr>"
- some refactoring
* add test cases
* deal with double spaces
* update docs
* add new failing test
* fix docs
* simplify implementation, update test & docs
* Fix docs