jabber: block warnings that we cannot fix

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
build: fix clang 3.4 build

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
build: fix gcc 4.7 compilation

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>
core: workaround for crash when configuration is not available

Signed-off-by: Rafał Malinowski <rafal.przemyslaw.malinowski@gmail.com>