Move repositories to 'repos/' subdirectory

This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.

Issue #1082

repos/base/run/util_mmio.run

@@ -0,0 +1,52 @@
+#
+# Build
+#
+
+build "core init test/util_mmio"
+
+#
+# Boot image
+#
+
+create_boot_directory
+
+install_config {
+	<config>
+		<parent-provides>
+			<service name="ROM"/>
+			<service name="RAM"/>
+			<service name="CPU"/>
+			<service name="RM"/>
+			<service name="CAP"/>
+			<service name="PD"/>
+			<service name="LOG"/>
+		</parent-provides>
+		<default-route>
+			<any-service> <parent/> </any-service>
+		</default-route>
+		<start name="test">
+			<binary name="test-util_mmio"/>
+			<resource name="RAM" quantum="10M"/>
+		</start>
+	</config>
+}
+
+build_boot_image "core init test-util_mmio"
+
+#
+# Execution
+#
+
+append qemu_args "-nographic -m 64"
+
+run_genode_until "Test done.*\n" 10
+
+#
+# Conclusion
+#
+
+grep_output {\[init -\> test\]}
+
+compare_output_to {
+	[init -> test] Test done
+}