Update dr_libs.

extras/dr_flac.h

 /*
 FLAC audio decoder. Choice of public domain or MIT-0. See license statements at the end of this file.
-dr_flac - v0.12.19 - 2020-08-30
+dr_flac - v0.12.20 - 2020-09-08
 
 David Reid - mackron@gmail.com
 
@@ -232,7 +232,7 @@ extern "C" {
 
 #define DRFLAC_VERSION_MAJOR     0
 #define DRFLAC_VERSION_MINOR     12
-#define DRFLAC_VERSION_REVISION  19
+#define DRFLAC_VERSION_REVISION  20
 #define DRFLAC_VERSION_STRING    DRFLAC_XSTRINGIFY(DRFLAC_VERSION_MAJOR) "." DRFLAC_XSTRINGIFY(DRFLAC_VERSION_MINOR) "." DRFLAC_XSTRINGIFY(DRFLAC_VERSION_REVISION)
 
 #include <stddef.h> /* For size_t. */
@@ -1828,14 +1828,15 @@ static DRFLAC_INLINE drflac_uint64 drflac__swap_endian_uint64(drflac_uint64 n)
         #error "This compiler does not support the byte swap intrinsic."
     #endif
 #else
-    return ((n & (drflac_uint64)0xFF00000000000000) >> 56) |
-           ((n & (drflac_uint64)0x00FF000000000000) >> 40) |
-           ((n & (drflac_uint64)0x0000FF0000000000) >> 24) |
-           ((n & (drflac_uint64)0x000000FF00000000) >>  8) |
-           ((n & (drflac_uint64)0x00000000FF000000) <<  8) |
-           ((n & (drflac_uint64)0x0000000000FF0000) << 24) |
-           ((n & (drflac_uint64)0x000000000000FF00) << 40) |
-           ((n & (drflac_uint64)0x00000000000000FF) << 56);
+    /* Weird "<< 32" bitshift is required for C89 because it doesn't support 64-bit constants. Should be optimized out by a good compiler. */
+    return ((n & ((drflac_uint64)0xFF000000 << 32)) >> 56) |
+           ((n & ((drflac_uint64)0x00FF0000 << 32)) >> 40) |
+           ((n & ((drflac_uint64)0x0000FF00 << 32)) >> 24) |
+           ((n & ((drflac_uint64)0x000000FF << 32)) >>  8) |
+           ((n & ((drflac_uint64)0xFF000000      )) <<  8) |
+           ((n & ((drflac_uint64)0x00FF0000      )) << 24) |
+           ((n & ((drflac_uint64)0x0000FF00      )) << 40) |
+           ((n & ((drflac_uint64)0x000000FF      )) << 56);
 #endif
 }
 
@@ -11772,6 +11773,9 @@ DRFLAC_API drflac_bool32 drflac_next_cuesheet_track(drflac_cuesheet_track_iterat
 /*
 REVISION HISTORY
 ================
+v0.12.20 - 2020-09-08
+  - Fix a compilation error on older compilers.
+
 v0.12.19 - 2020-08-30
   - Fix a bug due to an undefined 32-bit shift.
 

extras/dr_mp3.h

 /*
 MP3 audio decoder. Choice of public domain or MIT-0. See license statements at the end of this file.
-dr_mp3 - v0.6.16 - 2020-08-02
+dr_mp3 - v0.6.17 - 2020-09-28
 
 David Reid - mackron@gmail.com
 
@@ -95,7 +95,7 @@ extern "C" {
 
 #define DRMP3_VERSION_MAJOR     0
 #define DRMP3_VERSION_MINOR     6
-#define DRMP3_VERSION_REVISION  16
+#define DRMP3_VERSION_REVISION  17
 #define DRMP3_VERSION_STRING    DRMP3_XSTRINGIFY(DRMP3_VERSION_MAJOR) "." DRMP3_XSTRINGIFY(DRMP3_VERSION_MINOR) "." DRMP3_XSTRINGIFY(DRMP3_VERSION_REVISION)
 
 #include <stddef.h> /* For size_t. */
@@ -713,6 +713,8 @@ static __inline__ __attribute__((always_inline)) drmp3_int32 drmp3_clip_int16_ar
     __asm__ ("ssat %0, #16, %1" : "=r"(x) : "r"(a));
     return x;
 }
+#else
+#define DRMP3_HAVE_ARMV6 0
 #endif
 
 
@@ -4430,6 +4432,9 @@ counts rather than sample counts.
 /*
 REVISION HISTORY
 ================
+v0.6.17 - 2020-09-28
+  - Bring up to date with minimp3.
+
 v0.6.16 - 2020-08-02
   - Simplify sized types.