Appveyor: add compiler setup script.

scripts/appveyor/compiler_setup.bat

@@ -0,0 +1,40 @@
+@echo off
+
+:: Now we declare a scope
+Setlocal EnableDelayedExpansion EnableExtensions
+
+if not defined Configuration set Configuration=2015
+
+if "%Configuration%"=="MinGW" ( goto :mingw )
+
+set arch=x86
+
+if "%platform%" EQU "x64" ( set arch=x86_amd64 )
+
+if "%Configuration%"=="2015" (
+	set SET_VS_ENV="C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\vcvarsall.bat"
+)
+
+if "%Configuration%"=="2013" (
+	set SET_VS_ENV="C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\vcvarsall.bat"
+)
+
+if "%Configuration%"=="2012" (
+	set SET_VS_ENV="C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\vcvarsall.bat"
+)
+
+if "%Configuration%"=="2010" (
+	set SET_VS_ENV="C:\Program Files (x86)\Microsoft Visual Studio 10.0\VC\vcvarsall.bat"
+)
+
+if "%Configuration%"=="2008" (
+	set SET_VS_ENV="C:\Program Files (x86)\Microsoft Visual Studio 9.0\VC\vcvarsall.bat"
+)
+
+:: Visual Studio detected
+endlocal & call %SET_VS_ENV% %arch%
+goto :eof
+
+:: MinGW detected
+:mingw
+endlocal & set PATH=c:\mingw\bin;%PATH%