compat/endian: sync with GPUJPEG

ported changes from GPUJPEG, mostly cosmetic

For Win32 implementation, winsock2 is not used at all - Windows stdlib.h
contains _byteswap_* family so it is better to use these and not pull
the whole winsock2.h header struff (and also the winsock library but this
is irrelevannt for UG because we need to link with it unconditionally).

Author: MartinPulec

src/compat/endian.h

@@ -8,7 +8,7 @@
  * required by POSIX 2024.
  */
 /*
- * Copyright (c) 2025 CESNET
+ * Copyright (c) 2025 CESNET, zájmové sdružení právnických osob
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -40,8 +40,8 @@
  * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-#ifndef COMPAT_NET_H_A5D7C443_895D_465E_A46D_BF5E6DAA833F
-#define COMPAT_NET_H_A5D7C443_895D_465E_A46D_BF5E6DAA833F
+#ifndef COMPAT_ENDIAN_H_A5D7C443_895D_465E_A46D_BF5E6DAA833F
+#define COMPAT_ENDIAN_H_A5D7C443_895D_465E_A46D_BF5E6DAA833F
 
 #ifdef __APPLE__
         // https://github.com/zeromq/zmqpp/issues/164#issuecomment-246346344
@@ -72,15 +72,15 @@
             defined(_M_ARM64) || \
             (defined(__BYTE_ORDER__) && \
              __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__)
-                #include<winsock2.h>
+                #include <stdlib.h>
                 #ifndef be16toh
-                        #define be16toh(x) ntohs(x)
-                        #define be32toh(x) ntohl(x)
-                        #define be64toh(x) ntohll(x)
+                        #define be16toh(x) _byteswap_ushort(x)
+                        #define be32toh(x) _byteswap_ulong(x)
+                        #define be64toh(x) _byteswap_uint64(x)
 
-                        #define htobe16(x) htons(x)
-                        #define htobe32(x) htonl(x)
-                        #define htobe64(x) htonll(x)
+                        #define htobe16(x) _byteswap_ushort(x)
+                        #define htobe32(x) _byteswap_ulong(x)
+                        #define htobe64(x) _byteswap_uint64(x)
 
                         #define htole16(x) (x)
                         #define htole32(x) (x)
@@ -103,4 +103,4 @@
         #include <endian.h>
 #endif
 
-#endif // defined COMPAT_NET_H_A5D7C443_895D_465E_A46D_BF5E6DAA833F
+#endif // defined COMPAT_ENDIAN_H_A5D7C443_895D_465E_A46D_BF5E6DAA833F