from  Benoît Perrot  <benoit@lrde.epita.fr>

	Introduce unique_strings.
	
	* src/misc/unique_string.hh, src/misc/unique_string.cc:
	Declare and define the string uniquifier.
	* src/misc/test-unique_string.cc: Test it.
	* src/misc/Makefile.am: Update accordingly.
	* src/Makefile.am: Link with libmisc.a.
	* src/inst/section.hh, src/inst/label.hh: 
	Use misc::unique_string instead of std::string.
	* src/inst/label.cc: Empty it.