Added admin privilege check

Running this as a non-administrator appears to work at first, but the
changes wouldn't stick on my Win 8.1 system.  It's weird, but this
script needs to run as admin.

1-setup-path-win.bat

@@ -5,6 +5,13 @@ SET CMDLINERUNSTR=%SystemRoot%\system32\cmd.exe
 SET NEWPATH1="C:\MinGW\msys\1.0\bin"
 SET NEWPATH2="C:\MinGW\bin"
 
+:: Make sure we're running with administrator privileges
+NET SESSION >nul 2>&1
+IF ERRORLEVEL 1 (
+	ECHO FAILED. Run this script with administrator privileges.
+	GOTO ExitBatch
+)
+
 :: Make sure the second path exists. The first path won't be created until the second script is run
 IF NOT EXIST !NEWPATH2! (ECHO Path not found: %NEWPATH2% && GOTO ExitBatch)