Check arguments of well-known symbol functions

The Symbol.hasInstance and Symbol.toPrimitive tests now check for
expected argument values given to the user-defined functions.
Put some ES5 tests in comment strings

These tests thus no longer need explicit try-catch guards.
Added Firefox note to ES6 defaults results
Merge pull request #231 from webbedspace/hasinstance

Check arguments of Symbol.hasInstance and Symbol.toPrimitive user functions
Merge pull request #232 from webbedspace/es5-test-code

Put some ES5 tests in comment strings
Merge pull request #237 from webbedspace/defaults-footnotes

Added Firefox note to ES6 defaults results
ES6: Added tests for each Proxy handler

This adds tests for the Proxy get, set, has, deleteProperty,
getOwnPropertyDescriptor, defineProperty, getPrototypeOf,
setPrototypeOf, isExtensible, preventExtensions, enumerate, ownKeys,
apply and construct handlers.
EJS support is inferred from the source.

Also fixes a few other results for old Firefox versions.

Sorry that this diff looks terrible, but if you run `git diff
--minimal`, it more accurately reflects the changes.
Added missing property names to the Reflect test
Added a Proxy.revocable test
Updated Proxy tests to multi-line comment strings

NOTE: this commit only updates data-es6.js.
Checks for proxy handler arguments

Proxy handler functions' standard arguments are now checked a bit more
thoroughly in the tests.

Also added a note about a Firefox bug regarding proxy inheritance.