Cleanup excessive whitespace and use membership tests in code related to
loading of compilation units; semantics is unaffected.

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

gcc/ada/

	* lib-load.adb (Load_Unit): Remove excessive whitespace.
	* lib.adb (Is_Internal_Unit, Is_Predefined_Unit): Likewise.
	* par-ch10.adb (P_Compilation_Unit): Simplify with membership
	test.
	* par-load.adb (Load): Likewise.
	* uname.adb (Get_Unit_Name): Likewise.