Semantically neutral cleanup after the main fix for expansion of
attribute Priority.

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

gcc/ada/

	* einfo-utils.adb (Number_Entries): Refine type of a local variable.
	* exp_attr.adb (Expand_N_Attribute_Reference): Rename Conctyp to
	Prottyp; refactor repeated calls to New_Occurrence_Of; replace
	Number_Entries with Has_Entries.
	* exp_ch5.adb (Expand_N_Assignment_Statement): Likewise; remove Subprg
	variable (apparently copy-pasted from expansion of the attribute).