tempfile ignores $TMPDIR and refuses delete=True

tempfile.gettempdir()             # TMPDIR=/x: CPython '/x'; v451 '/tmp'
tempfile.NamedTemporaryFile()     # v451: runtime error, delete=True not supported

Fix (lib/rtl/tempfile.pas)

• gettempdir: CPython's candidate list, taking the first directory that exists and has write and search access (PalAccess, where CPython creates a probe file). Made absolute (os.path.abspath), with no trailing separator, and fixed by the first call, as CPython's tempfile.tempdir is. NamedTemporaryFile without dir= now creates in it, rather than in the RTL's fixed /tmp/.
• NamedTemporaryFile(delete=True): close() removes the file; a second close() does nothing. __enter__/__exit__ make with call close(). The object is still a name rather than an open handle (unit header, point 1), so the pattern of opening .name elsewhere works while it lives.
• Remaining difference, stated in the unit header: CPython also deletes when the object is collected. A Pascal object's destructor does not run when NilPy releases it, so a delete=True file that is never closed stays.

Measured (2026-09-29)

• test/test_nilpy_tempfile_gettempdir_follows_tmpdir.npy, run under five environments: TMPDIR with a trailing slash; TMPDIR missing so TEMP wins; TMP only, as dir/./; none set; and TMPDIR=/proc (unwritable), so TEMP wins. Each run equals CPython's. The previous library is wrong in four, and right only when nothing is set.
• test/test_nilpy_named_temporary_file_deletes_on_close.npy: default delete, close twice, dir equal to gettempdir, delete=False with suffix/prefix, with for both, and writing and reading .name inside the with. It equals CPython on x86-64 and i386. The previous library stops at the first call.