Integrate Debian packaging changes

debian/control:
* restructure to make it easier to incorporate further changes
* update package descriptions
* move build-depends to a proper place
* update project URL

debian/rules:
* use proper hardening syntax
* strip linker option without explicit shell invocation
* remove useless comment
* add extra cleanup

debian/: package documentation separately

debian/docs: remove empty file

debian/coryright: update to match Debian format

Change-Id: Ia7654d34730e9f269831612bfba70a1338ce29d3
Related: OS#1694
diff --git a/debian/libosmocore-doc.doc-base b/debian/libosmocore-doc.doc-base
new file mode 100644
index 0000000..b13b82d
--- /dev/null
+++ b/debian/libosmocore-doc.doc-base
@@ -0,0 +1,7 @@
+Document: libosmocore-doc
+Title: Documentation for the libosmocore library
+Section: Programming
+
+Format: HTML
+Index: /usr/share/doc/libosmocore/core/html/index.html
+Files: /usr/share/doc/libosmocore/core/html/*.html