using vala-mode and d-mode at the same time in emacs 24.5.1 on ubuntu 15.10

using vala-mode and d-mode at the same time in emacs 24.5.1 on ubuntu 15.10

[dan]

Hi All,

I have some code in vala and also some code in d (the d-programming language).

For vala, i'm using the vala-mode which is supplied as a package
in ubuntu 15.10.  I'm not sure how to identify the version beyond this:
The mode itself seems to be stored in
    /etc/emacs/site-start.d/50vala-mode-el.el
in ubuntu 15.10.

For d, i'm using d-mode.el version 201512060745, which is not from
an ubuntu package but from github
    https://github.com/Emacs-D-Mode-Maintainers/Emacs-D-Mode

The problem shows up when i try to execute a command such as
    emacs -nw my_file.vala my_file.d

The *Messages* buffer shows complaints like this

Eval error in the `c-lang-defconst' for `c-opt-identifier-prefix-key' in d-mode:
Error during redisplay: (jit-lock-function 1) signaled (void-variable regexp)
Eval error in the `c-lang-defconst' for `c-identifier-start' in d-mode:
Eval error in the `c-lang-defvar' or `c-lang-setver' for `c-identifier-start' (source eval): (invalid-function c-lang-const)
Error during redisplay: (jit-lock-function 1) signaled (wrong-type-argument stringp nil)

But note that i can edit a d file by itself with no error.

I'd appreciate any advice on how to solve this problem,
including pointers to the right places to discuss it,
or even how to just get better information identifying
the version of vala-mode that i'm using.

My emacs version is 24.5.1.

TIA!

dan