Kernel+Libraries: Don't include limits.h from LibELF/Validation.h

The fallout of this is that Kernel/Syscalls/execve.cpp doesn't have
access to ARG_MAX anymore, so move that definition to Kernel/API as well

Kernel/API/POSIX/sys/limits.h

@@ -25,4 +25,6 @@
 
 #define NGROUPS_MAX 32
 
+#define ARG_MAX 65536
+
 #define PTHREAD_STACK_MIN (64 * 1024) // 64KiB

Userland/Libraries/LibC/limits.h

@@ -62,8 +62,6 @@
 #define LLONG_WIDTH 64
 #define ULLONG_WIDTH 64
 
-#define ARG_MAX 65536
-
 #define SSIZE_MAX LONG_MAX
 
 #define LINK_MAX 4096

Userland/Libraries/LibELF/Validation.h

@@ -8,7 +8,6 @@
 
 #include <AK/StringBuilder.h>
 #include <LibC/elf.h>
-#include <limits.h>
 
 namespace ELF {