ash: [VAR] Fix poplocalvar leak

ash: [VAR] Fix poplocalvar leak

Upstream commit:

    Date: Tue, 25 May 2010 18:14:32 +0800
    [VAR] Fix poplocalvar leak

    When a variable is marked as local, we set VSTRFIXED on its vp
    recored.  However, poplocalvar never clears this flag for variables
    that were unset to begin with.  Thus if you ever made an unset
    variable local, it would get the VSTRFIXED bit and stick around
    forever.

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