Since APP_VERSION is different for every commit and almost all file
include settings.hpp, the whole project has to be rebuilt for every
commit. With this, hopefully, this can be greatly reduced and only
changed files need to be rebuilt. This will also help ccache
We need to have the version string available in multiple places not just
the source code. It is now hardcoded in the root CMakeLists.txt and all
files that need it will be configured with cmake.
This also removed the unecessary duality of GIT_TAG and APP_VERSION and
GIT_TAG_NAMESPACE and APP_VERSION_NAMESPACE.
Curl removed that header in 73a2fcea0b4adea6ba342cd7ed1149782c214ae3
([1])
http.cpp doesn't use anything from that header and compilation works for
fine with curl 7.54.1
Fixes#647
Ref:
[1]: 73a2fcea0b
