add 'deref' command.
separate commands more clearly.
cfg: change "CFG" to "Build".

makes the invoking name "cfg.Build", which makes much more sense.
debug: delete dead code, fix test to do something worthwhile.

also make bfd sort the symbol list from Symbols(), so we can find
symbols quickly.  Should probably go back and update all of the
myriad "find symbol" functions to just use sort.Search...
add some global config to the commands setup.
cfg: add the ability to filter graphs based on func name.

also refactored the c++ a bunch so that filtering isn't so gross.
cfg: add a 'Local' build and some refactoring.

abstract out the conversion of types from C to Go into a separate
function.  use new function in both implementations.

also add a test that makes sure we're building our CFGs
semi-correctly.
commands: new "cfg" and "symlist" commands.

for building the (local) control flow graph and list of symbols.
cmd: abstract out some CFG code, add 'whereami' command.

whereami figures out the current function from the instruction
pointer and identifies how 'deep' into that function the user is.
cfg: function to build edgelist representation.

need to determine the number of in-edges in a future algorithm,
it's a nightmare without an edge-based data structure.
cfg: add code to detect loop headers.
cfg: compute per-basic-block depth information.

where 'depth' is defined as the number of loops the basic block
is contained within.