pcm_resample: add function pcm_resample_float()

A version of the resampler that doesn't need int->float->int
conversion.

src/pcm_resample_internal.h

@@ -41,6 +41,14 @@ pcm_resample_lsr_init(struct pcm_resample_state *state);
 void
 pcm_resample_lsr_deinit(struct pcm_resample_state *state);
 
+const float *
+pcm_resample_lsr_float(struct pcm_resample_state *state,
+		       unsigned channels,
+		       unsigned src_rate,
+		       const float *src_buffer, size_t src_size,
+		       unsigned dest_rate, size_t *dest_size_r,
+		       GError **error_r);
+
 const int16_t *
 pcm_resample_lsr_16(struct pcm_resample_state *state,
 		    unsigned channels,