dokan_fuse: Ship pkg-config file

[Rondom]

We might want to ship a pkg-config file to simplify building against dokanfuse. At least during the cmake-install this is easy to accomplish.

http://www.kaizou.org/2014/11/typical-cmake-project/

I am not sure whether we can ship it with the installer, though. Reason: One can use pkg-config for compiling under Cygwin, MSYS or Windows. All three have different means of specifying the same path (C:\foo,/c/foo,/cygdrive/c/foo) and the LDFLAGS may also be different

[Rondom]

The instructions in the link above can be simplified by not using so many custom variables (PKG_CONFIG_). For example one can reuse CMAKE_INSTALL_INCLUDEDIR instead of defining a separate custom variable PKG_CONFIG_INCLUDEDIR.

In my opinion, we should probably not use the fuse name for our pkg-config-file. There are several different user space file system solution and our solution is not the original libfuse. We should respect the original libfuse (unlikely they ever accept patches bringing Windows-compatibility, but still) and also avoid a conflict with any alternative user-space FS solutions. I would like to hear other people's opinions on this, though.

[Rondom]

I opened PR #375.
It needs testing and some discussion about how to handle the fact that we are using the libfuse-name.