Some regression tests are failing on Windows

[forejtv]

When running make test on AppVeyor, the tests below fail. The reasons for this vary, sometimes it's a parsing problem caused by a compiler version, but other times it is an incorrect verification result.

I am creating this issue as a generic tickets, and then will create new "sub-issues" as I discover reasons for respective tests failing or when I need help with that.

Failing tests:

ansi-c\Forward_Declaration2
ansi-c\Incomplete_Type1
ansi-c\Union_Padding1
ansi-c\Universal_characters1
ansi-c\function_return1
ansi-c\gcc_attributes7
ansi-c\struct6
ansi-c\struct7
cbmc\Malloc23
cbmc\byte_update2
cbmc\byte_update3
cbmc\byte_update4
cbmc\byte_update5
cbmc\byte_update6
cbmc\byte_update7
cbmc\pipe1
cbmc\unsigned___int128
cpp\Decltype1
cpp\Decltype2
cpp\Function_Overloading1
cpp\enum2
cpp\enum7
cpp\enum8
cpp\nullptr1
cpp\sizeof1
cpp\static_assert1
cbmc-java\VarLengthArrayTrace1
cbmc-java\classpath1
cbmc-java\jar-file3
cbmc-java\tableswitch2