Scons: Remove Werror=False in SConscript files

This patch removes the overriding of "-Werror" in a handful of
cases. The code compiles with gcc 4.6.3 and clang 3.0 without any
warnings, and thus without any errors. There are no functional changes
introduced by this patch. In the future, rather than ypassing
"-Werror", address the warnings.

util/regress all passing (disregarding t1000 and eio)