Raise frame on backward search.

* tex.el (TeX-source-correlate-sync-source): Raise frame when
placing point on the source location.
Replace completing-read-multiple with TeX-completing-read-multiple.

* style/pst-node.el (LaTeX-pstnode-env-psmatrix): Replace
`completing-read-multiple' with `TeX-completing-read-multiple'.

* style/pstricks.el (LaTeX-package-parameters): Ditto.

* style/siunitx.el (LaTeX-arg-siunitx-unit): Ditto.
Use crm-separator as separator in XEmacs TeX-completing-read-multiple.

* tex.el (fboundp): Use `crm-separator' as separator in XEmacs
`TeX-completing-read-multiple' implementation.
Add prompt argument to TeX-read-key-val and TeX-arg-key-val.

* latex.el (TeX-read-key-val): Add `prompt' optional argument.
(TeX-arg-key-val): Ditto.
Better unbinding of SPC in LaTeX-arg-acro-key-val and LaTeX-arg-siunitx-unit.

* style/acro.el (LaTeX-arg-acro-key-val): Let-bind keymap with SPC
key binding removed, instead of defining a new key binding for
SPC.  Use `TeX-arg-key-val' instead of `multi-prompt-key-value'
and `TeX-argument-insert'.

* style/siunitx.el (LaTeX-arg-siunitx-unit): Let-bind keymap with
SPC key binding removed, instead of defining a new key binding for
SPC.