[Ada] Add formal function parameter equality to SPARK containers

[Ada] Add formal function parameter equality to SPARK containers

This patch adds a formal function parameter "=" (L, R : Element_Type) to
SPARK containers. The equality that is used by default for Element_Type
after this patch is the primitive equality and not the predefined any
more. It also allows to use any function with the appropriate signature
for the equality function.

2019-08-19  Joffrey Huguet  <huguet@adacore.com>

gcc/ada/

	* libgnat/a-cfdlli.ads, libgnat/a-cfhama.ads,
	libgnat/a-cfinve.ads, libgnat/a-cforma.ads,
	libgnat/a-cofove.ads, libgnat/a-cofuma.ads,
	libgnat/a-cofuve.ads: Add formal function parameter "=" (L, R :
	Element_Type) to the generic packages.

From-SVN: r274643