Removing unintentional disabling of Scheme load in main.
Fixing test-memory after sexp.c refactoring and improved stack traces.
Implement SEXP_MAX_ANALYZE_DEPTH
This fixes issue #89.
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 eval.c                   | 90 ++++++++++++++++++++++++++----------------------
 include/chibi/features.h |  4 +++
 2 files changed, 53 insertions(+), 41 deletions(-)
Updating ephemerons use a context local type id.
Disabling weak vectors for now.
Updating test targets.  "make test" now runs the R7RS test suite.
"make test-all" runs R7RS + libs + FFI.  "make test-dist" also
runs memory and build tests.
For now build tests just check the core.