Detect several definitions of the same label in a section.

	* src/inst/section.hh (register_label):
	Return false when label is already known in the section, true
	otherwise. Move implementation to...
	* src/inst/section.cc, src/inst/Makefile.am:
	This new file.
	* src/inst/data_section.hh, src/inst/data_section.cc,
	* src/inst/text_section.hh, src/inst/text_section.cc (define_label):
	Propagate status of register_label.
	* src/inst/program_builder.hh.gen.py:
	Generate an error when a label is defined more than once.
	* tests/solve/data-label-already-defined.s,
	* tests/solve/text-label-already-defined.s,
	* tests/solve/Makefile.am:
	Test it.

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

	Update test suite machinery.
	
	* tests/nolimips-check:
	Rename PSYFLAGS to NOLFLAGS.
	* tests/generate-ref.mk:
	Distribute reference output files.
	* tests/common.mk,
	* tests/lexical/Makefile.am, tests/lexical/check-lexical,
	* tests/runtime/Makefile.am, tests/runtime/check-runtime,
	* tests/syntax/Makefile.am, tests/syntax/check-syntax, 
	* tests/good/Makefile.am, tests/good/check-good,
	* tests/solve/Makefile.am, tests/solve/check-solve,
	* tests/unlimited/Makefile.am, tests/unlimited/check-unlimited,
	Use automake's TESTS_ENVIRONMENT variable to set Nolimips' flags.
	

from  Benoît Perrot  <benoit@lrde.epita.fr>
        * dev/inst-solver-gen.py,
        * dev/parse-asm-scan-gen.py,
        * src/inst/register.hh:
        Support generic register identifiers.
        * NEWS:
        Document it.
        * tests/lexical/unlimited-regs.s:
        Move to...
        * tests/solve/unlimited-regs.s:
        This file.
        * tests/lexical/Makefile.am,
        * tests/solve/Makefile.am:
        Update.