core: snapshot improvements (#2052)

* Moves how snapshots are supplied to the Isolate. Previously they were
  given by Behavior::startup_data() but it was only called once at
  startup. It makes more sense (and simplifies Behavior) to pass it to the
  constructor of Isolate.
* Adds new libdeno type deno_snapshot instead of overloading
  deno_buf.
* Adds new libdeno method to delete snapshot deno_snapshot_delete().
* Renames deno_get_snapshot() to deno_snapshot_new().
* Makes StartupData hold references to snapshots. This was implicit when
  it previously held a deno_buf but is made explicit now. Note that
  include_bytes!() returns a &'static [u8] and we want to avoid
  copying that.

1 files changed, 1 insertions, 0 deletions

diff --git a/core/libdeno/internal.h b/core/libdeno/internal.h
index 71cf731b6..ce8c63c56 100644
--- a/core/libdeno/internal.h
+++ b/core/libdeno/internal.h
@@ -169,6 +169,7 @@ static intptr_t external_references[] = {
     0};
 
 static const deno_buf empty_buf = {nullptr, 0, nullptr, 0, 0};
+static const deno_snapshot empty_snapshot = {nullptr, 0};
 
 Deno* NewFromSnapshot(void* user_data, deno_recv_cb cb);