safer public header

[Jeremy Whiting]

Hynek, all,

Here's a small patch to make libspeechd.h much easier to work with from C/C++ 
apps/libraries.  I just wrapped the definition of spd_debug in an #ifdef 
matching the #ifdef in the .c file. This way apps that define their own 
spd_debug can still include libspeechd.h (I'd really really like this to get 
into the next release so kttsd in kde 4.4 wont have to have weird #define 
spd_debug spd_debug2 hacks in it before including libspeechd.h)

thanks,

Jeremy