Compile Window output is limited, make it configurable

With 2.0.1 the output for the compile window has been limited to 10000 lines:

src/plugins/projectexplorer/compileoutputwindow.cpp::46

const int MAX_LINECOUNT = 10000;

I heard it has been adjusted to 50000 in the latest git master, but there is no reason in having this hardcoded. Please make it configurable with the option to turn this limit off completely.