BOTH-SIDE: fix case where limit from below is und, from above is bounded

BOTH-SIDE: fix case where limit from below is und, from above is bounded

(The opposite case where the limit from below is bounded and the limit
from above is und was not problematic.)

Commit df1748a8 had a bug which caused this specific case to yield ind
instead of und:

(%i1) limit(exp(1/x)*sin(1/x),x,0); /* correct */
(%o1) und

(%i2) limit(exp(-1/x)*sin(1/x),x,0); /* incorrect */
(%o2) ind

I misread the beginning of BOTH-SIDE and I thought the case where a
one-sided limit yielded und was taken care of, but that was only true
for one direction.

There have been no tests in the test suite where the limit from one
direction is und and from the other direction is something bounded.

No problems with the test suite, share test suite or rtest_translator.
New tests have been added to rtest_limit.