Remove PkgConfig dependence on Windows

PkgConfig works properly only on Linux. On Windows, it is part of the MSYS2 platform and there is no guarantee that it works properly; it is also not necessary.

Instead of using PkgConfig, a CMake module FindPkgVersionWin is introduced to find the version of a package from a config file.

find_pkg_version_win function is used to find the version of cerf package under Windows.

Related to issue #133 (closed)

cmake/commons/FindPkgVersionWin.cmake

@@ -59,13 +59,13 @@ function(find_pkg_version_win libname conffile paths output_var)
         PATHS "${_paths}" PATH_SUFFIXES "${_path_sfx}"
         DOC "Package configuration for ${_pkgconffile}")
 
-    if(${libname}_PATH)
-        message(STATUS "${_msghdr} '${_pkgconffile}' found in '${${libname}_PATH}'")
-    else()
+    if(NOT ${libname}_PATH)
         message(WARNING "${_msghdr} '${_pkgconffile}' not found in paths {${_paths}}")
         return()
     endif()
 
+    message(STATUS "${_msghdr} '${_pkgconffile}' found in '${${libname}_PATH}'")
+
     # extract the configuration information
     file(READ "${${libname}_PATH}/${_pkgconffile}" _conf)
     string(TOLOWER "${_conf}" _conf_lc)
@@ -78,6 +78,4 @@ function(find_pkg_version_win libname conffile paths output_var)
         message(WARNING "${_msghdr} ${_outvar} not found")
     endif ()
 
-    message(STATUS "${_msghdr} ${_outvar} => ${${_outvar}}")
-
 endfunction()