don't crash when dot util is not installed

set OPT.dot to False if dot is not installed, rather than having
latter code throw exceptions because the attribute doesn't exist
Support '-o' option with text format

print text stackdumps to the specified file descriptor instead of
always sending them to stdout
text output format works with python3

Fun with str and byte conversions to make python3 happy while
still keeping python2.7 compatibility.

Code for the html and dot output formats still needs the same
treatment in order to work with python3.
html output format works with python3

Fun with str and byte conversions to make python3 happy while
still keeping python2.7 compatibility.
dot output format works with python3

Fun with str and byte conversions to make python3 happy while
still keeping python2.7 compatibility.
path prune option works with python3

another conversion from str to bytes so that the match between
filename and prefix-to-be-pruned works
Be less picky about detecting breakpoint ack

When setting a lot of breakpoints, occasionally the response comes
back prefixed by a normal prompt instead of subprompt, meaning
plain '(gdb)' instead of '>>>(gdb)' --  this did not get stripped
by the subprompt pattern, leading to the breakpoint acknowledgement
being thrown away as junk.

Simple solution: relax the breakpoint ack detection to ignore
any leading junk. The breakpoint ack is a pretty strong pattern in
itself, so it's not like there should be any false positives,
and the volume of text being matched is not sufficient to care about
match() vs search().
Merge branch 'master' into python3-support

Conflicts:
	ftrace
Merge pull request #2 from VCTLabs/python3-support

Python3 support