Fix stage 2 library grade installation problem.

tools/bootcheck:
    Copy all of the files required by the prepare_grade_dir script
    into the stage 2 boehm_gc directory.
Fix the namepace cleanliness check on 32-bit MinGW.

configure.ac:
	On 32-bit MinGW systems, symbols are decorated
	with an underscore prefix.  (This is not the
	case for MinGW64.)
Delete some unused files the tests directory.

tests/Makefile.tests:
	Delete an old Makefile that was resurrected during the
	conversion from SVN.

tests/debugger/interactive.exp2:
	Delete a file that is not being used.
Fix failing decldebug tests.

tests/debugger/declarative/builtin_call_rep.exp:
	The current definition of the proc_defn_rep structure has
	an additional field.

tests/debugger/declarative/condition_bug.m:
	Replace the use of the now-deleted svmap module.

tests/debugger/declarative/condition_bug.exp:
	Update this to conform to the current definition of the
	I/O state in C grades.
Make a note that ThreadScope support is currently broken.

README.ThreadScope:
    As above.