[backport] SI-7470 implements fundep materialization

Backports 21a8c6c from the 2.11.x branch under -Xfundep-materialization
as per Miles Sabin's request. Thanks Miles!
pull request feedback
Include compiler flags from system property when interpreting pragma

When interpreting the #partest pragma in check files, also look for
compiler flags that were provided using the partest.scalac_opts system
property. That is, for example, when running

    SCALAC_OPTS="-Ydelambdafy:method" test/partest test/files/...
version number for 1.0.1 release
bump version number to next snapshot
Merge pull request #22 from lrytz/pragma

Include compiler flags from system property when interpreting pragma
SI-8474  Inconsistent behavior of patch method

Changed Iterator to be consistent with other collections.

Also fixed SeqViewLike to validate/constrain inputs.

No specific tests; quasi-comprehensive collection tests will cover this later.
SI-5254 running an empty scala script should succeed

The script runner made the assumption that "compilation succeeded"
implies "there is a Main class to run", but this can be wrong if the
script is empty (or only contains imports/comments).

The ScriptRunner now uses the ClassPath utility to check if there really
is a main class. If not, it doesn't try to run it and returns
peacefully. This also makes `scala -e ''` succeed.
print all scalac opts in log, also those provided through -Dpartest.scalac_opts
Fix assertThrows, and the behaviors that it shadowed

The test in StdNamesTest was introduced in cff8b569, where newTermName
would throw on a negative length. In b090f97 this was changed to fix
the negative length, but the test was not adapted (as it didn't fail).
-Ystatistics accepts a list of phases, cleanups in MultiChoiceSetting

MultiChoiceSetting and Xlint with its deprecated aliases is now a bit
simpler, but there's still room for improvement, as noted in comments.
SI-8806 Add lower bound check to Any lint

We already exclude the lint check for infer-any if
Any is somewhere explicit.

This commit adds lower bounds of type params to
the somewheres.

Motivated by:

```
scala> f"${42}"
<console>:8: warning: a type was inferred to be `Any`; this may indicate a programming error.
              f"${42}"
                  ^
res0: String = 42
```
Use Enumeration for MultiChoiceSetting

This is pretty easy, since a ValueSet is a BitSet.

When the setting is updated, recompute the current
set of values, which is cheap and succinct.

Checking a flag is also easy and fast.

Choices in MultiChoiceSettings may enable other choices.
Fix broken URL for MathJAX Javascript dependency.

Loaded using an DNS alias for the CDN, as per the
[instructions](http://docs.mathjax.org/en/latest/configuration.html)

I also switched from `latest` to `2.3-latest`, so that we don't
automatically perform major upgrades.
Address PR feedback, fix MultiChoiceSetting.contains
Make MultiChoiceSetting.compute easier to understand
Merge pull request #3939 from lrytz/ystats

-Ystatistics accepts a list of phases for which to print stats
Merge pull request #3801 from Ichoran/issue/8474

SI-8474  Inconsistent behavior of patch method
Merge pull request #3946 from gourlaysama/wip/t5254

SI-5254 running an empty scala script should succeed
Merge pull request #3967 from retronym/topic/mathjax

Fix broken URL for MathJAX Javascript dependency.