externals: Upgrade glad to latest version

* Also change some mentions to OpenGL 3.3 to 4.3

externals/glad/include/KHR/khrplatform.h

@@ -90,12 +90,20 @@
  *                                  int arg2) KHRONOS_APIATTRIBUTES;
  */
 
+#if defined(__SCITECH_SNAP__) && !defined(KHRONOS_STATIC)
+#   define KHRONOS_STATIC 1
+#endif
+
 /*-------------------------------------------------------------------------
  * Definition of KHRONOS_APICALL
  *-------------------------------------------------------------------------
  * This precedes the return type of the function in the function prototype.
  */
-#if defined(_WIN32) && !defined(__SCITECH_SNAP__)
+#if defined(KHRONOS_STATIC)
+    /* If the preprocessor constant KHRONOS_STATIC is defined, make the
+     * header compatible with static linking. */
+#   define KHRONOS_APICALL
+#elif defined(_WIN32)
 #   define KHRONOS_APICALL __declspec(dllimport)
 #elif defined (__SYMBIAN32__)
 #   define KHRONOS_APICALL IMPORT_C
@@ -145,6 +153,20 @@ typedef int64_t                 khronos_int64_t;
 typedef uint64_t                khronos_uint64_t;
 #define KHRONOS_SUPPORT_INT64   1
 #define KHRONOS_SUPPORT_FLOAT   1
+/*
+ * To support platform where unsigned long cannot be used interchangeably with
+ * inptr_t (e.g. CHERI-extended ISAs), we can use the stdint.h intptr_t.
+ * Ideally, we could just use (u)intptr_t everywhere, but this could result in
+ * ABI breakage if khronos_uintptr_t is changed from unsigned long to
+ * unsigned long long or similar (this results in different C++ name mangling).
+ * To avoid changes for existing platforms, we restrict usage of intptr_t to
+ * platforms where the size of a pointer is larger than the size of long.
+ */
+#if defined(__SIZEOF_LONG__) && defined(__SIZEOF_POINTER__)
+#if __SIZEOF_POINTER__ > __SIZEOF_LONG__
+#define KHRONOS_USE_INTPTR_T
+#endif
+#endif
 
 #elif defined(__VMS ) || defined(__sgi)
 
@@ -227,14 +249,21 @@ typedef unsigned short int     khronos_uint16_t;
  * pointers are 64 bits, but 'long' is still 32 bits. Win64 appears
  * to be the only LLP64 architecture in current use.
  */
-#ifdef _WIN64
+#ifdef KHRONOS_USE_INTPTR_T
+typedef intptr_t               khronos_intptr_t;
+typedef uintptr_t              khronos_uintptr_t;
+#elif defined(_WIN64)
 typedef signed   long long int khronos_intptr_t;
 typedef unsigned long long int khronos_uintptr_t;
-typedef signed   long long int khronos_ssize_t;
-typedef unsigned long long int khronos_usize_t;
 #else
 typedef signed   long  int     khronos_intptr_t;
 typedef unsigned long  int     khronos_uintptr_t;
+#endif
+
+#if defined(_WIN64)
+typedef signed   long long int khronos_ssize_t;
+typedef unsigned long long int khronos_usize_t;
+#else
 typedef signed   long  int     khronos_ssize_t;
 typedef unsigned long  int     khronos_usize_t;
 #endif