ash: [VAR] Fix poplocalvar on abnormal exit from function

ash: [VAR] Fix poplocalvar on abnormal exit from function

Upstream commit:

    Date: Thu, 27 May 2010 11:32:55 +0800
    [VAR] Fix poplocalvar on abnormal exit from function

    The new localvar code broke the abnormal exit from functions
    and built-ins by not restoring the original localvar state.

    This patch fixes this by storing the previous localvar state so
    that we always unwind correctly in case of an abnormal exit.

    Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>