4987 - support `browse_trace` tool in SubX

I've extracted it into a separate binary, independent of my Mu prototype.

I also cleaned up my tracing layer to be a little nicer. Major improvements:

- Realized that incremental tracing really ought to be the default.
  And to minimize printing traces to screen.

- Finally figured out how to combine layers and call stack frames in a
  single dimension of depth. The answer: optimize for the experience of
  `browse_trace`. Instructions occupy a range of depths based on their call
  stack frame, and minor details of an instruction lie one level deeper
  in each case.

Other than that, I spent some time adjusting levels everywhere to make
`browse_trace` useful.

1 files changed, 2 insertions, 2 deletions

diff --git a/subx/040---tests.cc b/subx/040---tests.cc
index 24819993..e6f2f489 100644
--- a/subx/040---tests.cc
+++ b/subx/040---tests.cc
@@ -26,13 +26,13 @@ test-foo:  # offset 7
   c3/return
 
 # check that code in test-foo ran (implicitly called by run-tests)
-+run: inst: 0x00000007
++run: 0x00000007 opcode: 01
 
 :(code)
 void create_test_function(program& p) {
   if (p.segments.empty()) return;
   segment& code = p.segments.at(0);
-  trace(99, "transform") << "-- create 'run-tests'" << end();
+  trace(3, "transform") << "-- create 'run-tests'" << end();
   vector<line> new_insts;
   for (int i = 0;  i < SIZE(code.lines);  ++i) {
     line& inst = code.lines.at(i);