Kernel+LibC: Move name length constants to Kernel/API from limits.h

Reduce inclusion of limits.h as much as possible at the same time.

This does mean that kmalloc.h is now including Kernel/API/POSIX/limits.h
instead of LibC/limits.h, but the scope could be limited a lot more.
Basically every file in the kernel includes kmalloc.h, and needs the
limits.h include for PAGE_SIZE.

Kernel/Process.cpp

@@ -18,6 +18,7 @@
 #    include <Kernel/Devices/KCOVDevice.h>
 #endif
 #include <Kernel/API/POSIX/errno.h>
+#include <Kernel/API/POSIX/sys/limits.h>
 #include <Kernel/Devices/NullDevice.h>
 #include <Kernel/FileSystem/Custody.h>
 #include <Kernel/FileSystem/OpenFileDescription.h>
@@ -38,7 +39,6 @@
 #include <Kernel/Thread.h>
 #include <Kernel/ThreadTracer.h>
 #include <Kernel/TimerQueue.h>
-#include <LibC/limits.h>
 
 namespace Kernel {