- introduce the concept of a project level setup header
`src/libssh2_setup.h`, that is used by `src`, `example` and `tests`
alike. Move there all common platform/compiler configuration from
`src/libssh2_priv.h`, individual sources and `CMakeFiles.txt` files.
Also move there our hand-crafted (= not auto-generated by CMake or
autotools) configuration `win32/libssh2-config.h`.
- `win32` directory is empty now, delete it.
- `Makefile.mk`: adapt to the above. Build-directory is the target
triplet, or any custom name set via `BLD_DIR`.
- sync header path order between build systems:
build/src -> source/src -> source/include
- delete redundant references to `windows.h`, `winsock2.h`,
`ws2tcpip.h`.
- delete unnecessary #includes, update order (`libssh2_setup.h` first,
`winsock2.h` first), simplify where possible.
This makes the code warning-free without `WIN32_LEAN_AND_MEAN`.
At the same time this patch applies this macro globally, to avoid
header bloat.
- example: add missing *nix header guards.
- example: fix misindented `HAVE_UNISTD_H` `#ifdef`s.
- set `WIN32` with all build-tools.
- set `HAVE_SYS_PARAM_H` in the hand-crafted config for MinGW.
To match auto-detection.
- move a source-specific macro to `misc.c` from `libssh2_priv.h`.
See the PR's individual commits for step-by-step updates.
Closes#932
