DWARF: move pessimistic DWARF version checks for imported entities

DWARF: move pessimistic DWARF version checks for imported entities

A check in dwarf2out_imported_module_or_decl prevents
DW_TAG_imported_module from being emitted as it was introduced in the
DWARFv3 standard. However, this also prevents valid strict DWARFv2
constructs such as DW_TAG_imported_declaration from being emitted in
dwarf2out_imported_module_or_decl_1.

The latter already protects the emission of newer DWARF tags with
appropriate checks, so the one in the former is redundant and
pessimistic.  This function is already called from places like
process_scope_var, which are not protected anyway.

This patch moves the check in dwarf2out_imported_module_or_decl so that
in strict DWARFv2 mode, tags like DW_TAG_imported_declaration are
emitted while DW_TAG_imported_module are not.

gcc/

	* dwarf2out.c (dwarf2out_imported_module_or_decl): Move DWARF
	version check to protect only DW_TAG_imported_module generation.

gcc/testsuite/

	* gnat.dg/debug7.adb, gnat.dg/debug7.ads: New testcase.

From-SVN: r240772