Replace dash by underscore in temp file names.

* org-babel-groovy-evaluate: replace '-' by '_' in temp file names.

Apparently, the JVM uses file names in the construction of names of internal
objects and dashes are illegal in that context. See

   https://stackoverflow.com/questions/48893994/groovy-in-org-mode-babel

for an example.

lisp/ob-groovy.el

@@ -84,12 +84,12 @@ in BODY as elisp."
   (when session (error "Sessions are not (yet) supported for Groovy"))
   (pcase result-type
     (`output
-     (let ((src-file (org-babel-temp-file "groovy-")))
+     (let ((src-file (org-babel-temp-file "groovy_")))
        (progn (with-temp-file src-file (insert body))
               (org-babel-eval
                (concat org-babel-groovy-command " " src-file) ""))))
     (`value
-     (let* ((src-file (org-babel-temp-file "groovy-"))
+     (let* ((src-file (org-babel-temp-file "groovy_"))
             (wrapper (format org-babel-groovy-wrapper-method body)))
        (with-temp-file src-file (insert wrapper))
        (let ((raw (org-babel-eval