Add primitive CPPLINT.cfg.

We'll add more things to this as we discover other warnings we don't
care about.

Change-Id: I408f688827cab0f74e055d8f1778069163663f0b
diff --git a/CPPLINT.cfg b/CPPLINT.cfg
new file mode 100644
index 0000000..560d791
--- /dev/null
+++ b/CPPLINT.cfg
@@ -0,0 +1,2 @@
+set noparent
+filter=-build/header_guard,-runtime/int,-readability/function