Move declaration of fluid_alloc() to fluidsynth_priv.h

Fixes build of opensles, oboe and coreaudio.

src/drivers/fluid_oboe.cpp

@@ -28,7 +28,6 @@ extern "C" {
 
 #include "fluid_adriver.h"
 #include "fluid_settings.h"
-#include "fluid_sys.h"
 
 } // extern "C"
 

src/utils/fluid_sys.h

@@ -750,6 +750,4 @@ static FLUID_INLINE void *fluid_align_ptr(const void *ptr, unsigned int alignmen
 
 #define FLUID_DEFAULT_ALIGNMENT (64U)
 
-void* fluid_alloc(size_t len);
-
 #endif /* _FLUID_SYS_H */

src/utils/fluidsynth_priv.h

@@ -188,6 +188,8 @@ typedef void (*fluid_rvoice_function_t)(void *obj, const fluid_rvoice_param_t pa
 #define FLUID_ARRAY_ALIGNED(_t,_n,_a) (_t*)FLUID_MALLOC((_n)*sizeof(_t) + ((unsigned int)_a - 1u))
 #define FLUID_ARRAY(_t,_n)           FLUID_ARRAY_ALIGNED(_t,_n,1u)
 
+void* fluid_alloc(size_t len);
+
 /* File access */
 #define FLUID_FOPEN(_f,_m)           fopen(_f,_m)
 #define FLUID_FCLOSE(_f)             fclose(_f)