[Ada] Fix portability issues in access to subprograms

[Ada] Fix portability issues in access to subprograms

This patch improves the portability of the code generated by the
compiler for access to subprograms. Written by Richard Kenner.

2019-09-18  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* exp_ch4.adb (Expand_N_Op_Eq): The frontend assumes that we can
	do a bit-for-bit comparison of two access to protected
	subprogram pointers. However, there are two reasons why we may
	not be able to do that: (1) there may be padding bits for
	alignment before the access to subprogram, and (2) the access to
	subprogram itself may not be compared bit-for- bit because the
	activation record part is undefined: two pointers are equal iff
	the subprogram addresses are equal. This patch fixes it by
	forcing a field-by-field comparison.
	* bindgen.adb (Gen_Adainit): The type No_Param_Proc is defined
	in the library as having Favor_Top_Level, but when we create an
	object of that type in the binder file we don't have that
	pragma, so the types are different. This patch fixes this issue.
	* libgnarl/s-interr.adb, libgnarl/s-interr__hwint.adb,
	libgnarl/s-interr__sigaction.adb, libgnarl/s-interr__vxworks.adb
	(Is_Registered): This routine erroneously assumes that the
	access to protected subprogram is two addresses. We need to
	create the same record that the compiler makes to ensure that
	any padding is the same. Then we have to look at just the first
	word of the access to subprogram. This patch fixes this issue.

From-SVN: r275856