configure: Disable warning C4703 with MSVC

This disables warnings about potentially uninitialized local pointer variables. Disabling the warning is in line with what we do for gcc.
8 years ago · 5bcc6f76f1
--- a/configure
+++ b/configure
@@ -3056,7 +3056,7 @@ msvc_flags(){
            -Wall)                echo -W4 -wd4244 -wd4127 -wd4018 -wd4389     \
                                       -wd4146 -wd4057 -wd4204 -wd4706 -wd4305 \
                                       -wd4152 -wd4324 -we4013 -wd4100 -wd4214 \
                                       -wd4273 -wd4554 -wd4701 ;;
                                       -wd4273 -wd4554 -wd4701 -wd4703 ;;
        esac
    done
 }