MSVC installation wrapper script

Per previous discussion with Magnus, the attached batch file (rename to
install.bat) is a wrapper script for the MSVC installer. It sets up the
environment before installing (to allow zic.exe to run properly), and
removes the need to explicitly call perl on the command line.

This should be added to src/tools/msvc

Regards, Dave.
@echo off
REM $PostgreSQL$

if NOT "%1"=="" GOTO RUN_INSTALL

echo Invalid command line options.
echo Usage: "install.bat <path>"
echo.
exit /b 1

:RUN_INSTALL

SETLOCAL
if exist src\tools\msvc\buildenv.bat call src\tools\msvc\buildenv.bat
if exist buildenv.bat call buildenv.bat

perl install.pl "%1"

exit /b %ERRORLEVEL%