Kernel/LibC: add mmap for private anonymous mappings

This will be used by the userspace to get more memory. Currently
kernel handles all allocations, which is not preferable.

libc/include/sys/mman.h

@@ -46,6 +46,16 @@ struct posix_typed_mem_info
 	size_t posix_tmi_length;	/* Maximum length which may be allocated from a typed memory object. */
 };
 
+struct sys_mmap_t
+{
+	void* addr;
+	size_t len;
+	int prot;
+	int flags;
+	int fildes;
+	off_t off;
+};
+
 int		mlock(const void* addr, size_t len);
 int		mlockall(int flags);
 void*	mmap(void* addr, size_t len, int prot, int flags, int fildes, off_t off);

libc/include/sys/syscall.h

@@ -55,6 +55,8 @@ __BEGIN_DECLS
 #define SYS_FSTATAT 48
 #define SYS_STAT 49 // stat/lstat
 #define SYS_SYNC 50
+#define SYS_MMAP 51
+#define SYS_MUNMAP 52
 
 __END_DECLS