[Ada] Fix LTO warning with tagged types

[Eric Botcazou]

Static dispatch tables use a trick to break up circularity problems: first 
they are declared as imported constants then defined as exported constants.
This leads to problems with type merging in LTO mode because a specific 
subtype is used in each case.

Tested on i586-suse-linux, applied on the mainline.


2010-05-08  Eric Botcazou  <ebotcazou@adacore.com>

	* exp_disp.adb (Make_Tags): Mark the imported view of dispatch tables.
	* gcc-interface/decl.c (gnat_to_gnu_entity) <E_Variable>: Make imported
	constants really constant.
	<E_Record_Subtype>: Strip the suffix for dispatch table entities.


2010-05-08  Eric Botcazou  <ebotcazou@adacore.com>

	* gnat.dg/lto5.adb: New test.
	* gnat.dg/lto5_pkg.ad[sb]: New helper.


-- 
Eric Botcazou
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