Add $EXEEXT to all linked programs in the new testsuite.

Add $EXEEXT to all linked programs in the new testsuite.

* tests/convenience.at, tests/ctor.at, tests/darwin.at,
tests/deplibs-ident.at, tests/duplicate_conv.at,
tests/duplicate_deps.at, tests/duplicate_members.at,
tests/export.at, tests/fail.at, tests/indirect_deps.at,
tests/inherited_flags.at, tests/link-order.at,
tests/link-order2.at, tests/lt_dladvise.at, tests/lt_dlexit.at,
tests/need_lib_prefix.at, tests/runpath-in-lalib.at,
tests/search-path.at, tests/shlibpath.at, tests/static.at,
tests/stresstest.at, tests/template.at, tests/testsuite.at:
Use $EXEEXT throughout, except in Makefile.am snippets where
automake takes care of it, and in testsuite macros that take
care of the extension.
Reports by Roumen Petrov and Alon Bar-Lev.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>