speedbar.el makes bootstrapping fail.

[Luc Teirlinck]

`speedbar-supported-extension-expressions' and `speedbar-file-regexp'
mutually use each other.  `speedbar-supported-extension-expressions'
used to be defined first.  This gave a compiler warning, but no other
trouble that I know of.  A few hours ago Richard changed the order of
the two functions, in as far as I know, to get rid of the compiler
warning.  But this makes bootstrapping fail.

Interchanging the order again solves that problem.  So I plan to do
that, to make bootstrapping work.

I am hesitant to put a `with-no-warnings' around the defcustom,
because the elisp manual says that def{var,const,custom} should be at
top level.  The patch below first gives a "fake" defvar for
`speedbar-file-regexp', then defcustoms
`speedbar-supported-extension-expressions', then gives the real
defvar for `speedbar-file-regexp'.  The compiler seems happy with that.

Any comments?  I probably want to commit reasonably quickly, since
bootstrapping is broken and any change I make can always be amended.

Sincerely,

Luc.