B3 trapping memory accesses should be documented

B3 trapping memory accesses should be documented
https://bugs.webkit.org/show_bug.cgi?id=162845

Reviewed by Geoffrey Garen.

Source/JavaScriptCore:

While writing some documentation, I found some small holes in the code.

* b3/B3Effects.cpp:
(JSC::B3::Effects::operator==): Need this to write tests.
(JSC::B3::Effects::operator!=): Need this to write tests.
* b3/B3Effects.h:
* b3/B3HeapRange.h:
* b3/B3MemoryValue.cpp:
(JSC::B3::MemoryValue::dumpMeta): Sometimes the heap range dump won't show you the memory value's actual range. This makes the dump show you the actual range in that case.
* b3/B3Value.cpp:
(JSC::B3::Value::effects): While documenting this, I remembered that trapping also has to imply reading top. I fixed this.
* b3/testb3.cpp:
(JSC::B3::testTrappingLoad): Added checks for the effects of trapping loads.
(JSC::B3::testTrappingStore): Added checks for the effects of trapping stores.
(JSC::B3::testMoveConstants): Made this not crash with validation.

Websites/webkit.org:

Added documentation for the Traps flag, and factored out the documentation of the Chill flag
to a new flags section.

* docs/b3/intermediate-representation.html:

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@206739 268f45cc-cd09-0410-ab3c-d52691b4dbfc