[Ada] Add support for check command in gnat driver

[Arnaud Charlet <charlet at adacore dot com>]

Tested on i686-linux, committed on trunk

The GNAT driver is modified so that when called with command Check and
switch -U, gnatcheck is invoked with all the sources of all the
projects.

Now also accept a new command CHECK to drive
the ASIS tool gnatcheck with a project file. If no source is specified,
gnatcheck is called with all the sources of the project.

2005-12-05  Vincent Celier  <celier@adacore.com>

	* gnatcmd.adb (GNATCmd): GNAT CHECK accepts switch -U
	If GNAT CHECK is called with a project file, but with no
	source on the command line, call gnatcheck with all the compilable
	sources of the project.
	Take into account the new command Check, for gnatcheck. Treat as for
	other ASIS tools: take into account project, specific package Check and
	Compiler switches.
	For ASIS tools, add the switches in package Compiler for
	the invocation of the compiler.

	* prj-attr.adb: Add package Check and its attributes

	* vms_conv.ads (Command_Type): New command Check, for gnatcheck

	* vms_conv.adb (Initialize): Change Params of command Check to
	unlimited files.
	Change some Hostparm.OpenVMS checks to Targparm.OpenVMS_On_Target.
	Add data for new command Check

	* vms_data.ads: Add project related qualifiers for GNAT CHECK and GNAT
	ELIM.
	Add qualifiers for Check command options
	(Command_Type): New command Check

Attachment: difs.17
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