The implicit parameter syntax adds a second parameter list
before the explicit parameter list when declaring macros, builtins and
runtime functions:

  extern macro MyMacro(implicit a: Smi)(b: Oddball);

when calling the macro, only the formal parameters can be provided
at the call site. The implicit parameters are implicitly looked-up
by name in the scope of the call and prepended to the explicit parameter
list. The values that are found by name for each implicit parameter must
be castable the corresponding implicit parameter type:

  MyMacro(Null);  // Error, a is not defined
  ...
  const a: Smi = 0;
  MyMacro(Null);  // OK
  ...
  const a: Object = 0;
  MyMacro(Null);  // Error, a has wrong type

For external macros, builtins and runtime functions, the formal
parameter list expected on the C++ side is the concatenation of the
implicit and explicit parameter lists.

As a drive-by: fix the formatting of typeswitch statements in the
the presence of deferred-marked blocks and funky white space.

Bug: v8:7793
Change-Id: I40da8405c706d7cdeca35367c9c954d0b33f6bf4
Reviewed-on: https://chromium-review.googlesource.com/c/1270996
Commit-Queue: Daniel Clifford <danno@chromium.org>
Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56555}