Two modifications:
1. The addition of 2013 to the copyright year range for every file;
2. The use of a single year range, instead of potentially multiple
year ranges, as approved by the FSF.
Including stdbool.h before hw-properties.h results in a build error due
to the hw_add_boolean_property function having an argument named "bool"
in its prototype. The source file has already be renamed to not use
this ("boolean" instead), so match the header to the source.
