Use the unified size types provided by the Genode tool chain.

diff --git src/lib/libc/sys/arm/include/_types.h src/lib/libc/sys/arm/include/_types.h
index 3012f97..3ec5a24 100644
--- src/lib/libc/sys/arm/include/_types.h
+++ src/lib/libc/sys/arm/include/_types.h
@@ -85,11 +85,11 @@ typedef	__int8_t	__int_least8_t;
 typedef	__int16_t	__int_least16_t;
 typedef	__int32_t	__int_least32_t;
 typedef	__int64_t	__int_least64_t;
-typedef	__int32_t	__ptrdiff_t;		/* ptr1 - ptr2 */
+typedef	__PTRDIFF_TYPE__	__ptrdiff_t;		/* ptr1 - ptr2 */
 typedef	__int32_t	__register_t;
 typedef	__int32_t	__segsz_t;		/* segment size (in pages) */
-typedef	__uint32_t	__size_t;		/* sizeof() */
-typedef	__int32_t	__ssize_t;		/* byte count or error */
+typedef	__SIZE_TYPE__	__size_t;		/* sizeof() */
+typedef	__PTRDIFF_TYPE__	__ssize_t;		/* byte count or error */
 typedef	__int64_t	__time_t;		/* time()... */
 typedef	__uint32_t	__uintfptr_t;
 typedef	__uint64_t	__uintmax_t;
diff --git src/lib/libc/sys/x86/include/_types.h src/lib/libc/sys/x86/include/_types.h
index 07893c6..abd2ea4 100644
--- src/lib/libc/sys/x86/include/_types.h
+++ src/lib/libc/sys/x86/include/_types.h
@@ -100,20 +100,20 @@ typedef	__int16_t	__int_least16_t;
 typedef	__int32_t	__int_least32_t;
 typedef	__int64_t	__int_least64_t;
 #ifdef	__LP64__
-typedef	__int64_t	__ptrdiff_t;		/* ptr1 - ptr2 */
+typedef	__PTRDIFF_TYPE__	__ptrdiff_t;		/* ptr1 - ptr2 */
 typedef	__int64_t	__register_t;
 typedef	__int64_t	__segsz_t;		/* segment size (in pages) */
-typedef	__uint64_t	__size_t;		/* sizeof() */
-typedef	__int64_t	__ssize_t;		/* byte count or error */
+typedef	__SIZE_TYPE__	__size_t;		/* sizeof() */
+typedef	__PTRDIFF_TYPE__	__ssize_t;		/* byte count or error */
 typedef	__int64_t	__time_t;		/* time()... */
 typedef	__uint64_t	__uintfptr_t;
 typedef	__uint64_t	__uintptr_t;
 #else
-typedef	__int32_t	__ptrdiff_t;
+typedef	__PTRDIFF_TYPE__	__ptrdiff_t;
 typedef	__int32_t	__register_t;
 typedef	__int32_t	__segsz_t;
-typedef	__uint32_t	__size_t;
-typedef	__int32_t	__ssize_t;
+typedef	__SIZE_TYPE__	__size_t;
+typedef	__PTRDIFF_TYPE__	__ssize_t;
 typedef	__int32_t	__time_t;
 typedef	__uint32_t	__uintfptr_t;
 typedef	__uint32_t	__uintptr_t;
