[Partial backport of r51218 | neal.norwitz -- the changes to ast.c, symtable.c,

[Partial backport of r51218 | neal.norwitz -- the changes to ast.c, symtable.c,
 and _elementtree.c weren't applicable]

Klocwork made another run and found a bunch more problems.
This is the first batch of fixes that should be easy to verify based on context.
This fixes problem numbers: 220 (ast), 323-324 (symtable),
321-322 (structseq), 215 (array), 210 (hotshot), 182 (codecs), 209 (etree).