examples : add missing #include <cstdint> (#798)

common.cpp uses uint8_t and uint64_t, which are defined in <cstdint>.

examples/common.cpp

@@ -6,6 +6,7 @@
 #include "dr_wav.h"
 
 #include <cmath>
+#include <cstdint>
 #include <regex>
 
 #ifndef M_PI