Replace SDL types by C99 standard types

Scrcpy is a C11 project. Use the C99 standard types instead of the
SDL-specific types:

    SDL_bool -> bool
    SintXX   -> intXX_t
    UintXX   -> uintXX_t

app/src/fps_counter.h

@@ -1,13 +1,14 @@
 #ifndef FPSCOUNTER_H
 #define FPSCOUNTER_H
 
-#include <SDL2/SDL_stdinc.h>
+#include <stdbool.h>
+#include <stdint.h>
 
 #include "config.h"
 
 struct fps_counter {
-    SDL_bool started;
-    Uint32 slice_start; // initialized by SDL_GetTicks()
+    bool started;
+    uint32_t slice_start; // initialized by SDL_GetTicks()
     int nr_rendered;
 #ifdef SKIP_FRAMES
     int nr_skipped;