Use CMake and support clients using CMake

[friendlyanon]

Fixes #3 and some compiler warnings. Moved WIN32_LEAN_AND_MEAN to the build system.

I have also seen someone wanting to add Linux support, which should be easy by just extending the if().

For anyone wanting to add tests to this, you'll just have to add these lines at the end:

include(CTest)
if(BUILD_TESTING)
  add_executable(CrashlogsTests test.cpp)
  target_link_libraries(CrashlogsTests PRIVATE Crashlogs)
  add_test(NAME CrashlogsTests COMMAND CrashlogsTests)
endif()

Lines 12-16 make it possible for users to consume this project like so:

find_package(Crashlogs REQUIRED)
target_link_libraries(Dog PRIVATE Crashlogs::Crashlogs)

#include <crashlogs.h>

...

Vendoring via add_subdirectory (or anything that wraps it) is NOT supported. That would require even more code for no good reason.

[friendlyanon]

Oops, sticky shift key.

[TylerGlaiel]

leave WIN32_LEAN_AND_MEAN in the file and I'll add it (reasoning: cmake should be completely optional)

[friendlyanon]

Would also be worth seeing where #4 goes. I could just rebase and adapt changes from that instead of having to do 2 PRs.

[TylerGlaiel]

sure, cmake is entirely irrelevant to me so if you wanna wait till mac/linux support is in to add it then let me know. im not gonna maintain cmakelists.txt myself, someone will have to update it when new platforms are added

[friendlyanon]

Seems the other PR went dormant. You could accept this then I can review CMake related changes in the other PR if it ever gets picked back up.