Debian package updates.

* Split out a new libgtp-dev package.
* Updated dependencies.
diff --git a/debian/libgtp.install b/debian/libgtp.install
index 88de30d..d0dbfd1 100644
--- a/debian/libgtp.install
+++ b/debian/libgtp.install
@@ -1,3 +1 @@
-usr/lib/libgtp.*
-usr/include/gtp.h
-usr/include/pdp.h
+usr/lib/lib*.so.*