frontend.adb: Update call to Unnest_Subprograms.

frontend.adb: Update call to Unnest_Subprograms.

2016-04-21  Javier Miranda  <miranda@adacore.com>

	* frontend.adb: Update call to Unnest_Subprograms.
	* exp_ch6.ads, exp_ch6.adb, exp_unst.ads, exp_unst.adb
	(Unnest_Subprograms): Moved to package exp_unst.
	* exp_unst.ads (Unnest_Subprogram): Moved to the body of the
	package.
	* exp_dbug.adb (Qualify_Entity_Name): Enable qualification of
	enumeration literals when generating C code.

From-SVN: r235303