[Etoys] Ogg Vorbis and Speex CODEC for Squeak eToys

[Takashi Yamamiya]

Bert,

> you need to make sure the VM compiles even without the headers and 
> libraries present. We need to have configure-time checks for all needed 
> headers and libraries, and disable the plugin if those are not present. 
> I see you check for the headers, but not for the libraries. There is an 
> AC_PLUGIN_CHECK_LIB macro for this, see doc/HowToBuildFromSource.txt

OK. I added a couple of AC_CHECK_LIBs because using both AC_TRY_COMPILE
and AC_PLUGIN_CHECK_LIB caused an error in disablePlugin.c. This is somewhat
ugly though, it seems to work well. I'm completely novice about the
syntax of acinclude.m4, so please check it.

> The proper way to make sure ogg or speex is installed would be in 
> sugar-jhbuild sanitycheck.

I'll take a look at that.

cheers,
- Takashi