Test patches for OS/2

Test patches for OS/2

a) Teaches tests in os2/OS2/*/* new format of $Config{extensions};
 os2/OS2/ExtAttr/t/os2_ea.t os2/OS2/PrfDB/t/os2_prfdb.t
 os2/OS2/REXX/t/rx_cmprt.t os2/OS2/REXX/t/rx_dllld.t
 os2/OS2/REXX/t/rx_objcall.t os2/OS2/REXX/t/rx_sql.test
 os2/OS2/REXX/t/rx_tiesql.test os2/OS2/REXX/t/rx_tievar.t
 os2/OS2/REXX/t/rx_tieydb.t os2/OS2/REXX/t/rx_varset.t
 os2/OS2/REXX/t/rx_vrexx.t

b) Closes all the files before unlinking - for DOSISH systems;
 t/cmd/while.t t/comp/multiline.t t/io/argv.t t/lib/anydbm.t
 t/lib/gdbm.t t/lib/ndbm.t t/lib/odbm.t t/lib/sdbm.t

c) t/README mentions running `harness' to get better granularity;
 t/README

d) New test op/lex_assign.t added - will check optimization of lexicals
	when applied - 153 cases (some just ignored since hard to implement).
 MANIFEST t/op/lex_assign.t

e) When a script is started via shell, $Config{exe_ext} may be appended.
 t/op/magic.t

f) path/echo may print a warning if run without args
 t/comp/colon.t

g) Error explanations more verbose
  t/op/cmp.t t/op/magic.t

p5p-msgid: <199701170448.XAA28948@monk.mps.ohio-state.edu>