[Ada] Optional section in ALI files for local cross-references

[Arnaud Charlet <charlet at adacore dot com>]

In ALFA mode, generate an additional section in ALI files for so-called 'local'
cross-references, which 1) group the cross-references in each subprogram or
package; 2) add references to object definitions ('D' or 'I' with
initialization). This new section should be used in specific back-ends which
need to compute the set of global variables read/written directly or not by a
subprogram.

Tested on x86_64-pc-linux-gnu, committed on trunk

2011-08-02  Yannick Moy  <moy@adacore.com>

	* lib-writ.adb (Write_ALI): when ALFA mode is set, write local
	cross-references section in ALI.
	* lib-xref.adb, lib-xref.ads (Xref_Entry): add components Sub
	(enclosing subprogram), Slc (location of Sub) and Sun (unit number of
	Sub).
	(Enclosing_Subprogram_Or_Package): new function to return the enclosing
	subprogram or package entity of a node
	(Is_Local_Reference_Type): new function returns True for references
	selected in local cross-references.
	(Lt): function extracted from Lt in Output_References
	(Write_Entity_Name): function extracted from Output_References
	(Generate_Definition): generate reference with type 'D' for definition
	of objects (object declaration and parameter specification), with
	appropriate locations and units, for use in local cross-references.
	(Generate_Reference): update fields Sub, Slc and Sun. Keep newly created
	references of type 'I' for initialization in object definition.
	(Output_References): move part of function Lt and procedure
	Write_Entity_Name outside of the body. Ignore references of types 'D'
	and 'I' introduced for local cross-references.
	(Output_Local_References): new procedure to output the local
	cross-references sections.
	(Lref_Entity_Status): new array defining whether an entity is a local
	* sem_ch3.adb (Analyze_Object_Declaration): call Generate_Reference
	with 'I' type when initialization expression is present.
	* get_scos.adb, get_scos.ads: Correct comments and typos

Attachment: difs
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