Use in_addr in ip_mreq_source and ip_msfilter.

This adds a new mechanism to say "replace struct S with #include <bits/S.h>".

Also switch epoll_event over to the new mechanism.

Also use the kernel's struct sockaddr_storage directly rather than behind
an unnecessary #define.

This patch also removes some dead code in the header scrubber. This code
still needs rewriting completely. I learned that a "block" isn't necessarily
a single struct definition, say; it might be a run of them. It seems like
a block is a run of preprocessor directives or a run of regular code.

Bug: https://issuetracker.google.com/36987220
Test: new test
Change-Id: Ic6a5c09559766a4babe3cd4c3ea538b885e07308
diff --git a/libc/kernel/uapi/rdma/rdma_user_cm.h b/libc/kernel/uapi/rdma/rdma_user_cm.h
index 81d963b..24e0f2e 100644
--- a/libc/kernel/uapi/rdma/rdma_user_cm.h
+++ b/libc/kernel/uapi/rdma/rdma_user_cm.h
@@ -82,7 +82,7 @@
   __u32 id;
   __u16 addr_size;
   __u16 reserved;
-  struct __kernel_sockaddr_storage addr;
+  struct sockaddr_storage addr;
 };
 struct rdma_ucm_resolve_ip {
   struct sockaddr_in6 src_addr;
@@ -96,8 +96,8 @@
   __u16 src_size;
   __u16 dst_size;
   __u32 reserved;
-  struct __kernel_sockaddr_storage src_addr;
-  struct __kernel_sockaddr_storage dst_addr;
+  struct sockaddr_storage src_addr;
+  struct sockaddr_storage dst_addr;
 };
 struct rdma_ucm_resolve_route {
   __u32 id;
@@ -129,8 +129,8 @@
   __u16 pkey;
   __u16 src_size;
   __u16 dst_size;
-  struct __kernel_sockaddr_storage src_addr;
-  struct __kernel_sockaddr_storage dst_addr;
+  struct sockaddr_storage src_addr;
+  struct sockaddr_storage dst_addr;
 };
 struct rdma_ucm_query_path_resp {
   __u32 num_paths;
@@ -208,7 +208,7 @@
   __u32 id;
   __u16 addr_size;
   __u16 join_flags;
-  struct __kernel_sockaddr_storage addr;
+  struct sockaddr_storage addr;
 };
 struct rdma_ucm_get_event {
   __u64 response;