[Ada] Code reorganization

[Ada] Code reorganization

This patch performs a code reorganization of the implementation of
pragma Compile_Time_Error. No functional change.

No test required.

2019-07-08  Javier Miranda  <miranda@adacore.com>

gcc/ada/

	* gnat1drv.adb (Post_Compilation_Validation_Checks:
	Validate_Compile_Time_Warning_Errors is now located in sem_prag
	(instead of sem_ch13).
	* sem_ch13.ads (Validate_Compile_Time_Warning_Error,
	Validate_Compile_Time_Warning_Errors): Move to sem_prag.
	* sem_ch13.adb
	(Compile_Time_Warnings_Errors): Move to sem_prag.
	(Initialize): Remove initialization of table
	Compile_Time_Warning_Errors.
	(Validate_Compile_Time_Warning_Error,
	Validate_Compile_Time_Warning_Errors): Move to sem_prag.
	* sem_prag.ads (Validate_Compile_Time_Warning_Errors): New
	procedure.
	* sem_prag.adb (Initialize): Initialize table
	Compile_Time_Warning_Errors.

From-SVN: r273202