Fix for CMake build type default flags being lost
Fix for CMake build type default flags being lost

The CMakeLists.txt adds -std=c++11 and related compiler flags, but looses default flags specified by CMake build type.
For example, -DCMAKE_BUILD_TYPE=Debug has no effect, as -g flag gets lost.

coldzhang/sqlpp11,rbock/sqlpp11,sergeken/sqlpp11,rbock/sqlpp-concepts-experiments,rbock/sqlpp11,happybits/sqlpp11,happybits/sqlpp11,rbock/sqlpp-concepts-experiments,rettichschnidi/sqlpp11,rettichschnidi/sqlpp11,volka/sqlpp11,sergeken/sqlpp11,coldzhang/sqlpp11,sergeken/sqlpp11,volka/sqlpp11,sergeken/sqlpp11,volka/sqlpp11,rbock/sqlpp11,happybits/sqlpp11,coldzhang/sqlpp11,volka/sqlpp11,happybits/sqlpp11,rettichschnidi/sqlpp11,rbock/sqlpp11,rettichschnidi/sqlpp11,rbock/sqlpp-concepts-experiments