re PR ada/38333 (Illegal program not detected, ARM 6.1(20): pragma Import illegal for abstract subprograms)

    gcc/ada/
	PR ada/38333
	* sem_prag.adb (Process_Import_Or_Interface): Forbid an abstract
	subprogram to be completed with a "pragma Import".

    gcc/testsuite/
	PR ada/38333
	* gnat.dg/specs/import_abstract.ads: New.

From-SVN: r152486