Miscellaneous amendments to the scratch/correct-warning-pos branch

Miscellaneous amendments to the scratch/correct-warning-pos branch

* lisp/cedet/semantic/fw.el (semantic-alias-obsolete)
(semantic-varalias-obsolete): Replace calls to byte-compile-warn with calls to
byte-compile-warn-x (when it exists).

* lisp/emacs-lisp/bytecomp.el (byte-compile-log-warning-function)
(byte-compile--log-warning-for-byte-compile): Make the POSITION parameter no
longer &optional (for the benefit of flymake on *.el).
(byte-compile-log-warning): Replace a nil POSITION argument with an actual
position.
(byte-compile-file-form-require): Push the required symbol onto
byte-compile-form-stack, for the benefit of `do-after-load-evaluation'.

* lisp/keymap.el (define-keymap--compile): Replace four calls to
byte-compile-warn with byte-compile-warn-x.

* doc/lispref/elisp.texi (master menu): Add entries for Shorthands and Symbols
with position.

* doc/lispref/streams.texi (Input Functions): Document
read-positioning-symbols.

* doc/lispref/symbols.texi (Symbols): Add new menu entry.
(Symbols with Position): New @section.