add random binaries to .gitignore

Signed-off-by: Jan III Sobieski <jan3sobi3ski@gmail.com>
Signed-off-by: Michal Marek <mmarek@suse.cz>

Documentation/.gitignore

+filesystems/dnotify_test
+laptops/dslm
+timers/hpet_example
+vm/hugepage-mmap
+vm/hugepage-shm
+vm/map_hugetlb
+

arch/x86/.gitignore

+boot/compressed/vmlinux
+tools/test_get_len
+