Fix compiler errors with the Speex resampler and -std=c89.

extras/speex_resampler/ma_speex_resampler.h

@@ -29,6 +29,16 @@ int ma_speex_resampler_get_expected_output_frame_count(SpeexResamplerState* st,
 #endif  /* ma_speex_resampler_h */
 
 #if defined(MINIAUDIO_SPEEX_RESAMPLER_IMPLEMENTATION)
+/* The Speex resampler uses "inline", which is not defined for C89. We need to define it here. */
+#if defined(__GNUC__) && !defined(_MSC_VER)
+    #if defined(__STRICT_ANSI__)
+        #if !defined(inline)
+            #define inline __inline__ __attribute__((always_inline))
+            #define MA_SPEEX_INLINE_DEFINED
+        #endif
+    #endif
+#endif
+
 #if defined(_MSC_VER) && !defined(__clang__)
     #pragma warning(push)
     #pragma warning(disable:4244)   /* conversion from 'x' to 'y', possible loss of data */
@@ -45,6 +55,11 @@ int ma_speex_resampler_get_expected_output_frame_count(SpeexResamplerState* st,
     #pragma GCC diagnostic pop
 #endif
 
+#if defined(MA_SPEEX_INLINE_DEFINED)
+    #undef inline
+    #undef MA_SPEEX_INLINE_DEFINED
+#endif
+
 EXPORT int ma_speex_resampler_get_required_input_frame_count(SpeexResamplerState* st, spx_uint64_t out_len, spx_uint64_t* in_len)
 {
     spx_uint64_t count;