use correct names for quasiquotation operators

Use #{`}#, #{,}# and #{,@}# as the quasiquote, unquote and
unquote-splicing operators, respectively. Previously they were named
escaping.

* module/language/elisp/compile-tree-il.scm (unquote?): Change "\," to
  "#{,}#".
  (unquote-splicing): Change "\,@" to "#{,@}#".
  (#{compile-`}#): Rename from #{compile-\`}#.
* module/language/elisp/runtime/function-slot.scm: Import #{compile-`}#
  instead of #{compile-\`}#, and re-export as #{`}# instead of as
  #{\`}#.
* module/language/elisp/parser.scm (quotation-symbols):
* test-suite/tests/elisp-compiler.test ("Eval", "Quotation"):
* test-suite/tests/elisp-reader.test ("Parser"): Change "\`", "\,", and
  "\,@" to "#{`}#", "#{,}#" and "#{,@}#", respectively.

module/language/elisp/parser.scm

@@ -165,9 +165,9 @@
 ;;; routine in our recursive-descent parser.
 
 (define quotation-symbols '((quote . quote)
-                            (backquote . \`)
-                            (unquote . \,)
-                            (unquote-splicing . \,@)))
+                            (backquote . #{`}#)
+                            (unquote . #{,}#)
+                            (unquote-splicing . #{,@}#)))
 
 (define (get-expression lex)
   (let* ((token (lex 'get))