Update readme file

readme.md

@@ -20,13 +20,12 @@ creation of simple drawings.
 ## <a name="install"></a>Installation
 
 After the release of **wxPdfDocument** version 0.9.5 the build support
-has been overhauled. The build files for Windows platforms is now
-generated by a (slightly modified) version of [Premake 5](https://premake.github.io/)
-(based on Premake 5.0 alpha 14).  
+has been overhauled. The build files for Windows platforms are now
+generated by [Premake 5](https://premake.github.io/) (based on Premake 5.0 alpha 14).  
 
 Ready to use project files are provided for Visual C++ 2010, 2012, 2013,
-2015, 2017, and 2019. Additionally, GNU Makefiles are provided supporting for
-example TDM-GCC MinGW.
+2015, 2017, and 2019. Additionally, GNU Makefiles are provided supporting
+MinGW-W64 GCC (version 7.3 or higher recommended) or TDM-GCC 5.1.
 
 For Visual Studio 2010+ solutions it is possible to customize the build
 by creating a `wx_local.props` file in the build directory which is used,
@@ -41,6 +40,27 @@ The customization files `wx_setup.props` resp. `config.gcc` allow to
 customize certain settings like for example the version number and the
 root directory of the wxWidgets library.
 
+#### **Note**
+The property file `wx_setup.props` in the `build` subdirectory was adjusted
+to allow running AppVeyor CI without any modifications.
+
+This modification triggers the use of specific library directories for
+different compiler versions (as it is used by the pre-built wxWidgets
+libraries). This adds the toolkit version (i.e. 141 for VS 2015,
+142 for VS 2019) to the library path name.
+
+For wxWidgets releases prior to version 3.1.3 this mode is not yet supported
+for VS 2019; for wxWidgets version 3.0.4 and below this affects also VS 2017.
+For those wxWidgets releases the wrong toolkit version is selected.
+
+To get the previous default behaviour (library path names without toolkit
+version) the 2 parameters _wxCompilerPrefix_ and _wxMsvcVersionAuto_ in
+file `wx_setup.props` have to be adjusted as follows:
+```xml
+<wxCompilerPrefix>vc</wxCompilerPrefix>
+<wxMsvcVersionAuto></wxMsvcVersionAuto>
+```
+
 ### wxMSW
 
 When building on Win32 or Win64, you can use the makefiles or one of the
@@ -51,6 +71,11 @@ debugging the sample applications should work right out of the box. For
 release builds you may need to copy the wxPdfDocument DLL or add the
 `lib` folder path to the Windows search path (PATH environment variable).
 
+#### **Note**
+Starting with version 0.9.8 **wxPdfDocument** uses specific compiler prefixes
+for its own library paths in its Windows build files, to allow parallel
+builds with different compiler versions.
+
 ### wxGTK
 
 When building on an autoconf-based system (like Linux/GNU-based