SI-7473 Bad for expr crashes postfix

This commit makes building PostfixSelect robust against a bad pos
on its operand, which can happen if a bad for expression results
in an EmptyTree.
SI-6138 Centralize and refine detection of `getClass` calls

`getClass` is special cased in the compiler; this is described
in in the comments on `Definitions.Any_getClass`.

Part of this happens in `Typer#stabilize`. This was trying to determine
if an Ident or Select node was a call to `getClass` by merits of the name
of the tree's symbol and by checking that the its type (if it was a
MethodType or PolyType) had no parameters in the primary parameter list.

Overloaded user defined `getClass` methods confused this check. In the
enclosed test case, the tree `definitions.this.getClass` had an
`OverloadedType`, and such types always report an empty list of `params`.

This commit:

  - changes `stabilize` to use `isGetClass`, rather than the
    homebrew check
  - changes `isGetClass` to consider a `Set[Symbol]` containing all
    `getClass` variants. This moves some similar code from `Erasure`
    to `Definitions`
  - keeps a fast negative path in `isGetClass` based on the symbol's name
SI-7509 Avoid crasher as erronous args flow through NamesDefaults

The fix for SI-7238 caused this regression.

This commit marks taints whole Apply with an ErrorType if it
has an erroneous argument, so as to stop a later crash trying
to further process the tree.
Merge pull request #2559 from soc/SI-7497

SI-7497 Fix scala.util.Properties.isMac
SI-7486 Regressions in implicit search.

Revert e86832d7e8 and dd33e280e2.
SI-7421 remove unneeded extra-attachement in maven deploy
Merge pull request #2595 from adriaanm/backport-pr-2450

SI-7421 remove unneeded extra-attachement in maven deploy
Merge pull request #2588 from retronym/ticket/7509

SI-7509 Avoid crasher as erronous args flow through NamesDefaults
Temporary reversion of a bit of d8b96bb858.

If I reverse these few lines, I can rebase miguel's
pull request cleanly; if I don't, git thinks there are
enough merge conflicts to start a war. Something is
suboptimal in that algorithm.
warn about uninitialized reads (in constructors), self-contained check

The check in question relies on helper maps and methods that don't
belong outside that check. This commit encapsulates those helpers into
the newly added `checkUninitializedReads()` , thus uncluttering
`transformClassTemplate()`
handling AnyVal special case early on to simplify logic afterwards

This way the contract of `transformClassTemplate()` can focus on
non-AnyVal cases, which are more regular from the perspective of
transforming their templates in the constructors phase.
how stuff works: elision of param-accessor-fields and outer-accessors
eliding what the constructor phase elides but with less effort (1 of 2)

For now both old and new implementations of elision coexist,
allowing cross-checking their results.
In the next commit only the new one will remain.
eliding what the constructor phase elides but with less effort (2 of 2)

Removing the old implementation of elision in constructors
in favor of the new one which is both faster, more readable.
method transformClassTemplate() turned into class TemplateTransformer
separation of concerns: delayed-init in constructors
separation of concerns: elision in constructors
readability for intoConstructors transformer
separation of concerns: guard non-specialized ctor-stats in constructors
skipping trips to specializeTypes when not necessary in constructors