lcUTF8: remove two unneeded ifs and two elses that are never reached

When there is a break at the end of the while loop, it means that the
loop will finish the first time that _XlcGetCharSetWithSide() returns
a non-NULL result, which means that the first '(last_charset == NULL)'
will always be true and the else part is redundant.

Fixes issue #46.

Reported-by: Bhavi Dhingra

Signed-off-by: Benno Schulenberg <bensberg@telfort.nl>
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