Use cast operators in headers to avoid warnings

This avoids compiler warnings when consuming the
headers from C++.

(cherry picked from commit 7381a2b072d8dbf6e596c45316d0eaba068d61df)

include/SDL3/SDL_events.h

@@ -1043,7 +1043,7 @@ typedef union SDL_Event
 } SDL_Event;
 
 /* Make sure we haven't broken binary compatibility */
-SDL_COMPILE_TIME_ASSERT(SDL_Event, sizeof(SDL_Event) == sizeof(((SDL_Event *)NULL)->padding));
+SDL_COMPILE_TIME_ASSERT(SDL_Event, sizeof(SDL_Event) == sizeof((SDL_static_cast(SDL_Event *, NULL))->padding));
 
 
 /* Function prototypes */

include/SDL3/SDL_rect.h

@@ -125,10 +125,10 @@ typedef struct SDL_FRect
  */
 SDL_FORCE_INLINE void SDL_RectToFRect(const SDL_Rect *rect, SDL_FRect *frect)
 {
-    frect->x = (float)rect->x;
-    frect->y = (float)rect->y;
-    frect->w = (float)rect->w;
-    frect->h = (float)rect->h;
+    frect->x = SDL_static_cast(float, rect->x);
+    frect->y = SDL_static_cast(float, rect->y);
+    frect->w = SDL_static_cast(float, rect->w);
+    frect->h = SDL_static_cast(float, rect->h);
 }
 
 /**

include/SDL3/SDL_stdinc.h

@@ -1164,7 +1164,7 @@ typedef struct SDL_alignment_test
     void *b;
 } SDL_alignment_test;
 SDL_COMPILE_TIME_ASSERT(struct_alignment, sizeof(SDL_alignment_test) == (2 * sizeof(void *)));
-SDL_COMPILE_TIME_ASSERT(two_s_complement, (int)~(int)0 == (int)(-1));
+SDL_COMPILE_TIME_ASSERT(two_s_complement, SDL_static_cast(int, ~SDL_static_cast(int, 0)) == SDL_static_cast(int, -1));
 #endif /* DOXYGEN_SHOULD_IGNORE_THIS */
 /** \endcond */
 
@@ -5921,7 +5921,7 @@ extern SDL_DECLSPEC char * SDLCALL SDL_iconv_string(const char *tocode,
  *
  * \since This macro is available since SDL 3.2.0.
  */
-#define SDL_iconv_utf8_ucs2(S)      (Uint16 *)SDL_iconv_string("UCS-2", "UTF-8", S, SDL_strlen(S)+1)
+#define SDL_iconv_utf8_ucs2(S)      SDL_reinterpret_cast(Uint16 *, SDL_iconv_string("UCS-2", "UTF-8", S, SDL_strlen(S)+1))
 
 /**
  * Convert a UTF-8 string to UCS-4.
@@ -5935,7 +5935,7 @@ extern SDL_DECLSPEC char * SDLCALL SDL_iconv_string(const char *tocode,
  *
  * \since This macro is available since SDL 3.2.0.
  */
-#define SDL_iconv_utf8_ucs4(S)      (Uint32 *)SDL_iconv_string("UCS-4", "UTF-8", S, SDL_strlen(S)+1)
+#define SDL_iconv_utf8_ucs4(S)      SDL_reinterpret_cast(Uint32 *, SDL_iconv_string("UCS-4", "UTF-8", S, SDL_strlen(S)+1))
 
 /**
  * Convert a wchar_t string to UTF-8.
@@ -5949,7 +5949,7 @@ extern SDL_DECLSPEC char * SDLCALL SDL_iconv_string(const char *tocode,
  *
  * \since This macro is available since SDL 3.2.0.
  */
-#define SDL_iconv_wchar_utf8(S)     SDL_iconv_string("UTF-8", "WCHAR_T", (char *)S, (SDL_wcslen(S)+1)*sizeof(wchar_t))
+#define SDL_iconv_wchar_utf8(S)     SDL_iconv_string("UTF-8", "WCHAR_T", SDL_reinterpret_cast(const char *, S), (SDL_wcslen(S)+1)*sizeof(wchar_t))
 
 
 /* force builds using Clang's static analysis tools to use literal C runtime