Move resolver public headers to separate include path

Additionally rename functions and structs to eliminate those ugly
underscores from the public API (with the notable exception of
__res_params, which will come in its own separate change to keep this
one from growing too large).

Test: build, flash, then 'atest netd_integration_test'
Change-Id: I7e9b0ee6cdbec889e9c35b5a17b5daa65533686e
diff --git a/resolv/resolv_static.h b/resolv/resolv_static.h
index 87bdce2..b250892 100644
--- a/resolv/resolv_static.h
+++ b/resolv/resolv_static.h
@@ -1,5 +1,5 @@
-#ifndef _RESOLV_STATIC_H_
-#define _RESOLV_STATIC_H_
+#ifndef NETD_RESOLV_STATIC_H
+#define NETD_RESOLV_STATIC_H
 
 #include <netdb.h>
 #include <stdio.h>
@@ -28,6 +28,6 @@
     struct hostent host;
 };
 
-res_static* res_get_static(void);
+res_static* res_get_static();
 
-#endif // _RESOLV_STATIC_H_
+#endif  // NETD_RESOLV_STATIC_H