(process) Runtime.exec(String cmd) can not parse legal command line

The current Runtime.exec(String cmd) uses wrong parser for command line. For
example. If given the comamnd line is exactly as below.
child.exe "a b"
Note there are two spaces between a and b. This command line will be parsed
into args like
argv[0] = "child.exe";
argv[1] = "\"a";
argv[2] = "b\"";

When these arguments are catenated together, what we got it
child "a b"
now, we have only one space between a and b. But there is only one space between
a and b in the orignal command line, we will lucky to get back the original one.

If it is on unix, we are totally screwed up. The child process will get 3
arguements instead of 2.