Fix travis 1.0.2 builds

Disable -Wshadow error when building with GCC
Add support for linu-x86_64-clang debug; this is needed for Travis CI.
Disable linux-clang and mingw debug builds on Travis CI; not supported.
Fix Travis email notifications config

Signed-off-by: Rich Salz <rsalz@openssl.org>
Reviewed-by: Andy Polyakov <appro@openssl.org>