Fix tc-let for mutable variables.

Closes PR 14415.
Add test case for PR 11747.

Closes PR 11747. This was fixed at some point.
Avoid a parameter for controlling resolve caching

The parameter dereference slowed down type-checking
new-metrics.rkt to about 28s from 16s on DrDr.

Instead of the parameter, explicitly remove items from the
cache during type alias setup.
Add test case for PR12985.

Closes PR 12985.
adjust #:enum arg to redex-check to be back like 6.0,
add #:uniform-at-random argument and #:in-order argument
change redex-check's default strategy to do both
enumeration and random generation in a manner
supported by our study
note redex-check change in redex history
Remove unused clause arguments in tc-let-unit.
Make let correctly implement the TC-Let rule from the paper.
fix performance problem in list-machine test suite

this was uncovered by the recent change to redex-check's
default strategy
Add invert-filter and use it in -imp.
Avoid division by 0 when there are no contract samples.
Refactor testing grammar.
Make TR random tester more robust against special values.
configure: test for large page sizes

Intended to fix PPC64 builds.
avoid compiler warnings
Reimplement shapes with borders to deal with transparency better.
Reorganize some code, fix beta PDF for a,x = 1,0 and b,x = 1,1
Added Brent-Dekker floating-point root finder
Made `real-dist-hpd-interval' return type more precise; documented