Fix configure error with older Boost versions

add_library() does not take libraries, target_link_libraries() does!

Some older boost libraries end up with flags such as "optimized" and
"debug" in the library list and CMake interpreted those as missing
source files with add_library().
Include ArxIO sources in style check
CMakeLists.txt: Use consistent variable names
Never add -fPIE to global CXX flags

Qt5 needs the arxcrashreporter code to be compile with -fPIE.
libArxIO needs to be build with -fPIC

GCC <= 4.7 don't like it when you use both of these flags at the
same time.

Change it so that -fPIE is only used on sources unique to the crash
reporter - ie the sources using Qt functions. This seems to be enough.
When a bow is equipped, hero screen shows the base damage from arrows.
The lower limit of player's Attributes and Stats is 1 now.
^GAMEDAYS variable now gets the amount of days, rather than their tens.
When a summoned creature kills an NPC, the player now receives experience points.
Set the default duration of "Confuse" spell to 5 seconds.