[Ada] Tidy up freezing code for instantiations
gcc/ada/
* sem_ch12.adb (Freeze_Subprogram_Body): Rename into...
(Freeze_Subprogram_Instance): ...this and change the name of the
first parameter and local variables for the sake of consistency.
(Insert_Freeze_Node_For_Instance): Use local variable Par_Inst.
(Install_Body): Rename into...
(Freeze_Package_Instance): ...this, remove first parameter and
change the name of local variables for the sake of consistency.
Do not deal with the special case of incomplete actual types here
and do not insert the body.
(Instantiate_Package_Body): Deal with the special case of incomplete
actual types here and insert the body. Call Freeze_Package_Instance
only if expansion is done.
(Instantiate_Subprogram_Body): Minor consistency tweak.