Be more consistent in using register-read-with-preview to read registers

Be more consistent in using register-read-with-preview to read registers

* frameset.el (frameset-to-register):
* kmacro.el (kmacro-to-register):
* register.el (increment-register):
* calc/calc-yank.el (calc-copy-to-register, calc-insert-register)
(calc-append-to-register, calc-prepend-to-register):
* play/gametree.el (gametree-layout-to-register)
(gametree-apply-register-layout):
* textmodes/picture.el (picture-clear-rectangle-to-register)
(picture-yank-rectangle-from-register):
* vc/emerge.el (emerge-combine-versions-register):
Use register-read-with-preview to read registers.

* cedet/semantic/senator.el (senator-copy-tag-to-register):
Use register-read-with-preview, if available.

* calculator.el, emulation/viper-cmd.el: Comments.