Update dr_flac and dr_wav.

extras/dr_wav.h

 /*
 WAV audio loader and writer. Choice of public domain or MIT-0. See license statements at the end of this file.
-dr_wav - v0.9.1 - 2019-05-05
+dr_wav - v0.9.2 - 2019-05-21
 
 David Reid - mackron@gmail.com
 */
@@ -2040,7 +2040,7 @@ drwav_bool32 drwav_init_ex(drwav* pWav, drwav_read_proc onRead, drwav_seek_proc
 
 drwav_uint32 drwav_riff_chunk_size_riff(drwav_uint64 dataChunkSize)
 {
-    if (dataChunkSize <= (0xFFFFFFFF - 36)) {
+    if (dataChunkSize <= (0xFFFFFFFFUL - 36)) {
         return 36 + (drwav_uint32)dataChunkSize;
     } else {
         return 0xFFFFFFFF;
@@ -2049,10 +2049,10 @@ drwav_uint32 drwav_riff_chunk_size_riff(drwav_uint64 dataChunkSize)
 
 drwav_uint32 drwav_data_chunk_size_riff(drwav_uint64 dataChunkSize)
 {
-    if (dataChunkSize <= 0xFFFFFFFF) {
+    if (dataChunkSize <= 0xFFFFFFFFUL) {
         return (drwav_uint32)dataChunkSize;
     } else {
-        return 0xFFFFFFFF;
+        return 0xFFFFFFFFUL;
     }
 }
 
@@ -2121,7 +2121,7 @@ drwav_bool32 drwav_init_write__internal(drwav* pWav, const drwav_data_format* pF
         so for the sake of simplicity I'm not doing any validation for that.
         */
         if (pFormat->container == drwav_container_riff) {
-            if (initialDataChunkSize > (0xFFFFFFFF - 36)) {
+            if (initialDataChunkSize > (0xFFFFFFFFUL - 36)) {
                 return DRWAV_FALSE; /* Not enough room to store every sample. */
             }
         }
@@ -3195,8 +3195,8 @@ void drwav_u8_to_s16(drwav_int16* pOut, const drwav_uint8* pIn, size_t sampleCou
     size_t i;
     for (i = 0; i < sampleCount; ++i) {
         int x = pIn[i];
-        r = x - 128;
-        r = r << 8;
+        r = x << 8;
+        r = r - 32768;
         pOut[i] = (short)r;
     }
 }
@@ -4675,6 +4675,9 @@ void drwav_free(void* pDataReturnedByOpenAndRead)
 /*
 REVISION HISTORY
 ================
+v0.9.2 - 2019-05-21
+  - Fix warnings.
+
 v0.9.1 - 2019-05-05
   - Add support for C89.
   - Change license to choice of public domain or MIT-0.