* [BUILD] Add build system module GENLINK, update README how to use it.

mk/genlink-rules.mk

@@ -0,0 +1,25 @@
+##
+## This file is part of the libopencm3 project.
+##
+## Copyright (C) 2014 Frantisek Burian <BuFran@seznam.cz>
+##
+## This library is free software: you can redistribute it and/or modify
+## it under the terms of the GNU Lesser General Public License as published by
+## the Free Software Foundation, either version 3 of the License, or
+## (at your option) any later version.
+##
+## This library is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU Lesser General Public License for more details.
+##
+## You should have received a copy of the GNU Lesser General Public License
+## along with this library.  If not, see <http://www.gnu.org/licenses/>.
+##
+
+$(LDSCRIPT):$(OPENCM3_DIR)/ld/linker.ld.S
+ifeq ($(GENLINK_DEFS),)
+	$(error unknown device $(DEVICE) for the linker. Cannot generate ldscript)
+endif
+	@printf "  GENLNK  $@\n"
+	$(Q)$(CPP) $(GENLINK_DEFS) -P -E $< > $@