Add commands stack and mem to ARM simulator debugger

Add commands stack and mem to ARM simulator debugger

The command "stack" will dump the stack and "mem" will dump memory from a address given either as a register or as a literal. Both commands dump 10 words unless an additional argument with the number of words to dump is given.
  sim> stack
  sim> mem fp
  sim> mem 0xe612a450 100

Also parse address literals in simulator debugger command as unsigned.
Review URL: http://codereview.chromium.org/1596022

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4388 ce2b1a6d-e550-0410-aec6-3dcde31c8c00