pcm_resample: renamed implementation functions

Added diversion functions to pcm_resample.c.  These check which
resampler is enabled at compile time (libsamplerate or fallback).
This prepares the following patch.

src/pcm_resample_internal.h

@@ -0,0 +1,79 @@
+/*
+ * Copyright (C) 2003-2009 The Music Player Daemon Project
+ * http://www.musicpd.org
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+/** \file
+ *
+ * Internal declarations for the pcm_resample library.  The "internal"
+ * resampler is called "fallback" in the MPD source, so the file name
+ * of this header is somewhat unrelated to it.
+ */
+
+#ifndef MPD_PCM_RESAMPLE_INTERNAL_H
+#define MPD_PCM_RESAMPLE_INTERNAL_H
+
+#include "pcm_resample.h"
+#include "config.h"
+
+#ifdef HAVE_LIBSAMPLERATE
+
+void
+pcm_resample_lsr_deinit(struct pcm_resample_state *state);
+
+const int16_t *
+pcm_resample_lsr_16(struct pcm_resample_state *state,
+		    uint8_t channels,
+		    unsigned src_rate,
+		    const int16_t *src_buffer, size_t src_size,
+		    unsigned dest_rate,
+		    size_t *dest_size_r);
+
+const int32_t *
+pcm_resample_lsr_32(struct pcm_resample_state *state,
+		    uint8_t channels,
+		    unsigned src_rate,
+		    const int32_t *src_buffer,
+		    G_GNUC_UNUSED size_t src_size,
+		    unsigned dest_rate,
+		    size_t *dest_size_r);
+
+#else
+
+void
+pcm_resample_fallback_deinit(struct pcm_resample_state *state);
+
+const int16_t *
+pcm_resample_fallback_16(struct pcm_resample_state *state,
+			 uint8_t channels,
+			 unsigned src_rate,
+			 const int16_t *src_buffer, size_t src_size,
+			 unsigned dest_rate,
+			 size_t *dest_size_r);
+
+const int32_t *
+pcm_resample_fallback_32(struct pcm_resample_state *state,
+			 uint8_t channels,
+			 unsigned src_rate,
+			 const int32_t *src_buffer,
+			 G_GNUC_UNUSED size_t src_size,
+			 unsigned dest_rate,
+			 size_t *dest_size_r);
+
+#endif
+
+#endif