Remove Variant unary negation and unary plus @override-unit-failures

These are only used for constant folding in the frontend.
Change stuff to do it there the way we actually implement them at
runtime.
Implement most bitwise arithmetic outside of Variant

Everything except unary bitwise not.
Implement shift operators outside of Variant
Translate some trivial cases of IncDecL

These are easy, so why not.
Revert "Fix duplicate HTTP headers"

This reverts commit e265247f34572eedd087ee01c8e43bdab319b322.
Replace _ with - in file names under runtime/vm/jit/

Makes things more consistent, at least within this directory.
Add client connect info to the debugger usage log.

Update the connect usage log message to include details of the client that is connecting to a proxy, or to state if it's a connection due to script debugging.
Update php_base64_decode() to cover Bug52327

Strict mode should fail on padding characters mid-stream.
Fix url rewriting

Only apply pathTranslation if a path hasn't been rewritten
(they're always relative paths), or if the rewritten path
didn't begin with '/'.
Update url_raw_encode() to ignore '~' characters

Per Bug#53248, tilde characters should
not be encoded.
Translate FPushFuncU

We were punting on this, but it's a pretty easy
translation, and it makes calling functions from inside namespaces
much faster.

Closes #814
Trace declared instance properties of objects

Instance properties were being completely ignored,
so the heap graph was missing a lot of information.
Turn off extended type hint checks
Fix (disable) reporting of extended typehints via reflection

Right now (on trunk, not release), a function with a ?int
typehint tells the reflection API its typehint is just "int".  For
now, just turn this off.  (If we want this later we'll probably have
to add a new API or something?)
Add skeleton.sh script for making extension skeletons from idl.json files