Fixes #156. Fix callstack management and display.#163

Merged

faultyserver merged 2 commits intomyst-lang:masterfrom faultyserver:fix/callstack

Feb 18, 2018

+531-58

Commits on Feb 16, 2018

[spec] Add add_breakpoint spec helper to make assertions during code execution.
faultyserver
committed

Commits on Feb 18, 2018

[spec,interpreter,parser] Fix callstack management and display.
faultyserver
committed