Remove unnecessary CMake definition
Remove unnecessary CMake definition

Remove unnecessary definition PQXX_SHARED

When building a shared library, define PQXX_SHARED in CMakeLists.txt of libpqxx.

Remove unnecessary definition WINDOWS_EXPORT_ALL_SYMBOLS

API symbols declared `__declspec(dllexport)`.

Remove unnecessary property CXX_STANDARD

Exist `set(CMAKE_CXX_STANDARD 11)` in CMakeLists.txt of libpqxx.

jgsogo/conan-libpqxx,jgsogo/conan-libpqxx,jgsogo/conan-libpqxx