Add the new macro with-suppressed-warnings

Add the new macro with-suppressed-warnings

* lisp/emacs-lisp/byte-run.el (with-suppressed-warnings): New macro.

* doc/lispref/compile.texi (Compiler Errors): Document
with-suppressed-warnings and deemphasise with-no-warnings
slightly.

* lisp/emacs-lisp/bytecomp.el (byte-compile--suppressed-warnings):
New internal variable.
(byte-compile-warning-enabled-p): Heed
byte-compile--suppressed-warnings, bound via with-suppressed-warnings.
(byte-compile-initial-macro-environment): Provide a macro
expansion of with-suppressed-warnings.
(byte-compile-file-form-with-suppressed-warnings): New byte hunk
handler for the suppressed symbol machinery.
(byte-compile-suppressed-warnings): Ditto for the byteop.
(byte-compile-file-form-defmumble): Ditto.
(byte-compile-form, byte-compile-normal-call)
(byte-compile-normal-call, byte-compile-variable-ref)
(byte-compile-set-default, byte-compile-variable-set)
(byte-compile-function-form, byte-compile-set-default)
(byte-compile-warn-obsolete, byte-compile--declare-var): Pass the
symbol being warned in to byte-compile-warning-enabled-p.

* test/lisp/emacs-lisp/bytecomp-tests.el (test-suppression): New
function.
(bytecomp-test--with-suppressed-warnings): Tests.