Rewrite ML_(fd_allowed):

* include explaination from Tom
* make logic easier to follow, and add comments
* remove veto on the -d file descriptor (detailed comments in code)



git-svn-id: svn://svn.valgrind.org/valgrind/trunk@4860 a5019735-40e9-0310-863c-91ae7b9d1cf9
1 file changed