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/FindPkgVersion.cmake

@@ -47,7 +47,7 @@ function(find_pkg_version_win libname conffile paths output_var)
 
     # initialize the output variable
     set(_outvar ${output_var})
-    if(NOT "${_outvar}")
+    if(NOT _outvar)
         set(_outvar ${libname}_VERSION)
     endif()
     set(${_outvar} "${_outvar}-NOTFOUND" PARENT_SCOPE)
@@ -71,8 +71,11 @@ function(find_pkg_version_win libname conffile paths output_var)
     string(TOLOWER "${_conf}" _conf_lc)
     string(REGEX MATCH "version[: \t]*([1-9.]+)" _rxmatch ${_conf_lc})
 
-    if("${CMAKE_MATCH_1}")
+    if(CMAKE_MATCH_1)
         set(${_outvar} "${CMAKE_MATCH_1}" PARENT_SCOPE)
+        message(STATUS "${_msghdr} ${_outvar} => ${CMAKE_MATCH_1}")
+    else()
+        message(WARNING "${_msghdr} ${_outvar} not found")
     endif ()
 
 endfunction()