Take arg specifying msdos or winnt batch file config.

From-SVN: r9005

gcc/configure.bat

-@echo off
-config\msdos\configure %1 %2 %3 %4
+@echo off
+if %1.==msdos. goto call_msdos
+if %1.==winnt. goto call_winnt
+echo Usage: configure msdos or configure winnt
+goto END
+
+:call_msdos
+call config\msdos\configure %1 %2 %3 %4
+goto END
+
+:call_winnt
+call config\i386\config-nt %1 %2 %3 %4
+goto END
+
+:END