[or-cvs] Add an autoconf test to make sure that memset(&ptr, 0, size...

[Nick Mathewson]

Update of /home/or/cvsroot
In directory moria.mit.edu:/tmp/cvs-serv15448

Modified Files:
	configure.in 
Log Message:
Add an autoconf test to make sure that memset(&ptr, 0, sizeof(ptr)) and ptr=NULL are equivalent