Kernel/LibC: Add ppoll syscall and fix poll

poll is now using its own syscall instead of wrapping aroung pselect.
This adds less overhead on top of poll and adds support for POLLHUP

userspace/libraries/LibC/include/sys/syscall.h

@@ -73,6 +73,7 @@ __BEGIN_DECLS
 	O(SYS_CONNECT,			connect)		\
 	O(SYS_LISTEN,			listen)			\
 	O(SYS_PSELECT,			pselect)		\
+	O(SYS_PPOLL,			ppoll)			\
 	O(SYS_TRUNCATE,			truncate)		\
 	O(SYS_SMO_CREATE,		smo_create)		\
 	O(SYS_SMO_DELETE,		smo_delete)		\