C++: Avoid repetitive calls

Change-Id: I6f04b98c14567d344907ac635df7eeee2f7aeac7
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>
qbs build: set minimum OS X version for autotests

Change-Id: I5ef9956f78da4096d25851951551dca633471fc0
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
CppTools: Deduplicate null validation

Change-Id: I291fd7d755f08a533bb2686024858b11fabd9bed
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>
CppTools: Pass some const variables by reference

Change-Id: I3e703c923f6e1a14a89c76f394a070184db0c7bf
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>