g-soccon-vms.ads: Fix value of MSG_WAITALL.

2007-10-15  Thomas Quinot  <quinot@adacore.com>

	* g-soccon-vms.ads: Fix value of MSG_WAITALL.

	* gen-soccon.c: 
	Update documentation to note that OpenVMS 8.3 or later must be used
	to generate g-soccon-vms.ads.

	* atree.adb: Add ??? comment

	* exp_util.adb: Minor reformatting.
	Add ??? comment in Kill_Dead_Code.

From-SVN: r129342