Some patches to compile with gcc-next

[Douglas Bagnall]

I wrote:

> In this case it looks like this test is using snprintf to truncate on
> purpose, and that is fine. For this I modified the relevant
> wscript_build to disable the error. At first I thought I needed to use
> "-Wno-format-length", but it seems "-Wformat-length" also does the
> trick by turning the -Werror back into a warning.

Unfortunately this fails on GCC 5.4 and is thus a bad solution.
"-Wno-format-length" does work though.

Douglas