busybox

shell: tweak bkslash_in_varexp.tests, add bkslash_in_varexp1.tests

It turns out bkslash_in_varexp.tests was a bash bug :]

ash and hush fail "corrected" bkslash_in_varexp.tests as well,
just not as badly as I thought (hush gets half of the cases right).

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>