Send thunks to check-syntax for type tooltips

This avoids the cost of computing the printed types
to some degree. It still does have overhead (~5%) over
not computing anything related to tooltips because of
the cost of traversing the type table and computing
tooltip locations.
add the get-autowrap-bitmap-width method to text%
adjust the wrap-bitmap-width field to always have an inexact number
try to take the autowrap bitmap into account when sizing the repl input box
document setup/main-doc
make path->relative-string/library use "<doc>/...." prefixes files in the docs
simplify the drracket/check-syntax documentation a little
XFORM_END_SKIP -> XFORM_SKIP_PROC in example.

The XFORM_SKIP_PROC example incorrectly used XFORM_END_SKIP,
it should have used XFORM_SKIP_PROC instead.
Fix/add base-env types for Ref 14.4.3
db: add empty string test for "text" type
simplify paths before using as hash keys
small tweaks to raco show-dependencies

- print '#%kernel instead of (quote #%kernel)
- add -l for more human-friendly output that shows direct requires
change set/c default #:kind to dont-care, to match docs

- add set/c tests
restore set/c default #:kind to 'immutable; update tests and docs to match
fix typos in "Building New Contract Combinators" guide
redex: record nt syntax info for extended language
redex: differentiate nts from different langauges
redex: keep syntax info for nt aliases
Add suppport for weak boxes in TR

Closes PR 14771
Fix ordering issue in typechecking inner calls

Closes PR 14810