of 'breakpoint command add/list/remove' commands to set breakpoint callbacks,
list them, and then remove one.

Modified the lldbtest.TestBase.expect() method to add two additional keyword
arguments:

o matching (default to True), which, if set to False, reverses the semantics of
  'expect' to 'expect not'

o patterns (default to None), which specifies a list of regexp patterns to match
  against the output from running the command

TestBreakpointCommand.py uses the matching=False and the patterns=[...] expect()
API.

llvm-svn: 114480