org-babel: Fix smart `replace-regexp-in-string' behavior during variable assignment

* lisp/ob-latex.el (org-babel-expand-body:latex):
* lisp/ob-lilypond.el (org-babel-expand-body:lilypond):
* lisp/ob-org.el (org-babel-expand-body:org):
* lisp/ob-sql.el (org-babel-sql-expand-vars): Pass FIXEDCASE and
LITERAL arguments to `replace-regexp-in-string'.  This avoids changing
case and special handling of \N constructs in the replacement string.

lisp/ob-latex.el

@@ -136,7 +136,7 @@ exporting the literal LaTeX source."
                  (regexp-quote (format "%S" (car pair)))
                  (if (stringp (cdr pair))
                      (cdr pair) (format "%S" (cdr pair)))
-                 body)))
+                 body t t)))
 	(org-babel--get-vars params))
   (let ((prologue (cdr (assq :prologue params)))
         (epilogue (cdr (assq :epilogue params))))

lisp/ob-lilypond.el

@@ -142,7 +142,7 @@ blocks.")
 	       (replace-regexp-in-string
 		(concat "$" (regexp-quote name))
 		(if (stringp value) value (format "%S" value))
-		body))))
+		body t t))))
      vars)
     (concat
      (and prologue (concat prologue "\n"))

lisp/ob-org.el

@@ -51,7 +51,7 @@ $VAR instances are replaced by VAR values defined in PARAMS."
     (setq body (replace-regexp-in-string
 		(regexp-quote (format "$%s" (car var)))
 		(format "%s" (cdr var))
-		body nil 'literal)))
+		body 'fixedcase 'literal)))
   
   (let ((prologue (cdr (assq :prologue params)))
         (epilogue (cdr (assq :epilogue params))))

lisp/ob-sql.el

@@ -411,7 +411,7 @@ argument mechanism."
                                                       (format "%S" el))))))))
                     data-file)
                 (if (stringp val) val (format "%S" val))))
-	    body)))
+	    body t t)))
    vars)
   body)