Clean up and document our hacks for building BSD source.

Change-Id: Ic591e22fa5b363bb68376b9f25814c0e5bd83fbf
diff --git a/libc/upstream-openbsd/README.txt b/libc/upstream-openbsd/README.txt
new file mode 100644
index 0000000..9db64ea
--- /dev/null
+++ b/libc/upstream-openbsd/README.txt
@@ -0,0 +1,5 @@
+This directory contains upstream OpenBSD source. You should not edit these
+files directly. Make fixes upstream and then pull down the new version of
+the file.
+
+TODO: write a script to make this process automated.
diff --git a/libc/upstream-openbsd/gdtoa_support.cpp b/libc/upstream-openbsd/android/gdtoa_support.cpp
similarity index 100%
rename from libc/upstream-openbsd/gdtoa_support.cpp
rename to libc/upstream-openbsd/android/gdtoa_support.cpp
diff --git a/libc/upstream-openbsd/arith.h b/libc/upstream-openbsd/android/include/arith.h
similarity index 100%
rename from libc/upstream-openbsd/arith.h
rename to libc/upstream-openbsd/android/include/arith.h
diff --git a/libc/upstream-openbsd/gd_qnan.h b/libc/upstream-openbsd/android/include/gd_qnan.h
similarity index 100%
rename from libc/upstream-openbsd/gd_qnan.h
rename to libc/upstream-openbsd/android/include/gd_qnan.h
diff --git a/libc/upstream-openbsd/openbsd-compat.h b/libc/upstream-openbsd/android/include/openbsd-compat.h
similarity index 100%
rename from libc/upstream-openbsd/openbsd-compat.h
rename to libc/upstream-openbsd/android/include/openbsd-compat.h
diff --git a/libc/upstream-openbsd/thread_private.h b/libc/upstream-openbsd/android/include/thread_private.h
similarity index 100%
rename from libc/upstream-openbsd/thread_private.h
rename to libc/upstream-openbsd/android/include/thread_private.h