Removed SDL_bool in favor of plain bool

We require stdbool.h in the build environment, so we might as well use the plain bool type.

If your environment doesn't have stdbool.h, this simple replacement will suffice:
typedef signed char bool;

test/testshader.c

@@ -23,7 +23,7 @@
 
 #include <SDL3/SDL_opengl.h>
 
-static SDL_bool shaders_supported;
+static bool shaders_supported;
 static int current_shader = 0;
 
 enum
@@ -128,7 +128,7 @@ static PFNGLSHADERSOURCEARBPROC pglShaderSourceARB;
 static PFNGLUNIFORM1IARBPROC pglUniform1iARB;
 static PFNGLUSEPROGRAMOBJECTARBPROC pglUseProgramObjectARB;
 
-static SDL_bool CompileShader(GLhandleARB shader, const char *source)
+static bool CompileShader(GLhandleARB shader, const char *source)
 {
     GLint status = 0;
 
@@ -148,13 +148,13 @@ static SDL_bool CompileShader(GLhandleARB shader, const char *source)
             SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to compile shader:\n%s\n%s", source, info);
             SDL_free(info);
         }
-        return SDL_FALSE;
+        return false;
     } else {
-        return SDL_TRUE;
+        return true;
     }
 }
 
-static SDL_bool LinkProgram(ShaderData *data)
+static bool LinkProgram(ShaderData *data)
 {
     GLint status = 0;
 
@@ -176,13 +176,13 @@ static SDL_bool LinkProgram(ShaderData *data)
             SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Failed to link program:\n%s", info);
             SDL_free(info);
         }
-        return SDL_FALSE;
+        return false;
     } else {
-        return SDL_TRUE;
+        return true;
     }
 }
 
-static SDL_bool CompileShaderProgram(ShaderData *data)
+static bool CompileShaderProgram(ShaderData *data)
 {
     const int num_tmus_bound = 4;
     int i;
@@ -196,18 +196,18 @@ static SDL_bool CompileShaderProgram(ShaderData *data)
     /* Create the vertex shader */
     data->vert_shader = pglCreateShaderObjectARB(GL_VERTEX_SHADER_ARB);
     if (!CompileShader(data->vert_shader, data->vert_source)) {
-        return SDL_FALSE;
+        return false;
     }
 
     /* Create the fragment shader */
     data->frag_shader = pglCreateShaderObjectARB(GL_FRAGMENT_SHADER_ARB);
     if (!CompileShader(data->frag_shader, data->frag_source)) {
-        return SDL_FALSE;
+        return false;
     }
 
     /* ... and in the darkness bind them */
     if (!LinkProgram(data)) {
-        return SDL_FALSE;
+        return false;
     }
 
     /* Set up some uniform variables */
@@ -234,12 +234,12 @@ static void DestroyShaderProgram(ShaderData *data)
     }
 }
 
-static SDL_bool InitShaders(void)
+static bool InitShaders(void)
 {
     int i;
 
     /* Check for shader support */
-    shaders_supported = SDL_FALSE;
+    shaders_supported = false;
     if (SDL_GL_ExtensionSupported("GL_ARB_shader_objects") &&
         SDL_GL_ExtensionSupported("GL_ARB_shading_language_100") &&
         SDL_GL_ExtensionSupported("GL_ARB_vertex_shader") &&
@@ -268,24 +268,24 @@ static SDL_bool InitShaders(void)
             pglShaderSourceARB &&
             pglUniform1iARB &&
             pglUseProgramObjectARB) {
-            shaders_supported = SDL_TRUE;
+            shaders_supported = true;
         }
     }
 
     if (!shaders_supported) {
-        return SDL_FALSE;
+        return false;
     }
 
     /* Compile all the shaders */
     for (i = 0; i < NUM_SHADERS; ++i) {
         if (!CompileShaderProgram(&shaders[i])) {
             SDL_LogError(SDL_LOG_CATEGORY_APPLICATION, "Unable to compile shader!\n");
-            return SDL_FALSE;
+            return false;
         }
     }
 
     /* We're done! */
-    return SDL_TRUE;
+    return true;
 }
 
 static void QuitShaders(void)