Fix undefined type error in libs/json11/json11.cpp

Under certain conditions, compilation errors out with
the following message:

    "error: ‘uint8_t’ does not name a type"

Explicitly including <cstdint> prevents that situation.

Signed-off-by: Gabriel Somlo <[email protected]>

Author: gsomlo

libs/json11/json11.cpp

@@ -24,6 +24,7 @@
 #include <cmath>
 #include <cstdlib>
 #include <cstdio>
+#include <cstdint>
 #include <limits>
 
 namespace json11 {