Remove inclusion of header files that we can't rely on due to portability

Some non-portable includes are left because they are already suitably
guarded.

Reviewed-by: Bernd Edlinger <bernd.edlinger@hotmail.de>
(Merged from https://github.com/openssl/openssl/pull/5105)

crypto/ec/curve448/arch_x86_64/arch_intrinsics.h

@@ -7,7 +7,7 @@
 
 #define ARCH_WORD_BITS 64
 
-#include <stdint.h>
+#include <openssl/e_os2.h>
 
 /* FUTURE: autogenerate */
 static __inline__ __uint128_t widemul(const uint64_t *a, const uint64_t *b) {

crypto/ec/curve448/curve448utils.h

@@ -12,8 +12,6 @@
 #ifndef __DECAF_COMMON_H__
 #define __DECAF_COMMON_H__ 1
 
-#include <stdint.h>
-#include <sys/types.h>
 #include <openssl/e_os2.h>
 
 #ifdef __cplusplus

crypto/ec/curve448/word.h

@@ -8,7 +8,7 @@
 #include <string.h>
 
 #include <assert.h>
-#include <stdint.h>
+#include <openssl/e_os2.h>
 #include "arch_intrinsics.h"
 
 #include "curve448utils.h"
@@ -24,8 +24,6 @@
 #include "portable_endian.h"
 
 #include <stdlib.h>
-#include <sys/types.h>
-#include <inttypes.h>
 
 #if defined(__ARM_NEON__)
 #include <arm_neon.h>