Trac #15236,#15237,#15238,#15239

Error out instead of continued processing when we already know the preprocessor directives are bungled.
Generally be more careful about the order in which cpp->elsetracker and cpp->ifdepth are checked/operated on.
Validate all accesses of cpp->elsedepth to ensure no out of bounds accesses occur.
Also slipped in a few indentation/spacing fixes.

Signed-off-by: Nicolas Capens

git-svn-id: https://angleproject.googlecode.com/svn/trunk@540 736b8ea6-26fd-11df-bfd4-992fa37f6226