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, 1 insertions, 1 deletions

diff --git a/021check_instruction.cc b/021check_instruction.cc
index 6347dfb3..5bc7fa9c 100644
--- a/021check_instruction.cc
+++ b/021check_instruction.cc
@@ -13,7 +13,7 @@ Transform.push_back(check_instruction);  // idempotent
 
 :(code)
 void check_instruction(const recipe_ordinal r) {
-  trace(9991, "transform") << "--- perform checks for recipe " << get(Recipe, r).name << end();
+  trace(101, "transform") << "--- perform checks for recipe " << get(Recipe, r).name << end();
   map<string, vector<type_ordinal> > metadata;
   for (int i = 0;  i < SIZE(get(Recipe, r).steps);  ++i) {
     instruction& inst = get(Recipe, r).steps.at(i);