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-codezero/Makefile

@@ -0,0 +1,54 @@
+#
+# \brief  Download and prepare the Codezero kernel
+# \author Norman Feske
+# \date   2011-08-05
+#
+
+VERBOSE    ?= @
+ECHO        = @echo
+GIT_URL     = https://github.com/nfeske/codezero.git
+GIT_REV     = 6fa4884a5a1cf6207372f69ae01e5faa6d5a39c8
+CONTRIB_DIR = contrib
+PATCHES     = $(shell find patches -name *.patch)
+
+#
+# Utility to check if a tool is installed
+#
+check_tool = $(if $(shell which $(1)),,$(error Need to have '$(1)' installed.))
+
+$(call check_tool,git)
+$(call check_tool,patch)
+$(call check_tool,python2.6)
+$(call check_tool,scons)
+
+#
+# Print help information by default
+#
+help::
+
+prepare: $(CONTRIB_DIR)
+
+help::
+	$(ECHO)
+	$(ECHO) "Check out upstream source code of the Codezero kernel"
+	$(ECHO)
+	$(ECHO) "The source code will be located at the '$(CONTRIB_DIR)/' directory."
+	$(ECHO)
+	$(ECHO) "--- available commands ---"
+	$(ECHO) "prepare - checkout upstream source codes"
+	$(ECHO) "clean   - remove upstream source codes"
+	$(ECHO)
+
+$(CONTRIB_DIR)/.git:
+	$(VERBOSE)git clone $(GIT_URL) $(CONTRIB_DIR)
+
+$(CONTRIB_DIR): $(CONTRIB_DIR)/.git
+	$(VERBOSE)cd $(CONTRIB_DIR); git reset --hard $(GIT_REV)
+	$(ECHO) "applying patches to '$(CONTRIB_DIR)/'"
+	$(VERBOSE)for i in $(PATCHES); do patch -d $@ -p1 < $$i; done
+
+.PHONY: $(CONTRIB_DIR)
+
+clean::
+	$(VERBOSE)rm -rf $(CONTRIB_DIR)
+