Let qtserialport load libudev at runtime

Setting the LOAD_LIBUDEV define makes sure qtserialport in 5.2 tries
to dynamically load libudev.so.

Change-Id: I62f0b011376c7b94e9c7c82cca30404a30ce61b9
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>
Add -debug-and-release option iOS configuration files

Task-number: QTBUG-34625

Change-Id: I681af9b06323a2e5afa2c428ddeb39e4dc271ffb
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>