[Ada] Fix bogus style check failure with pragma Style_Checks (Off)

[Ada] Fix bogus style check failure with pragma Style_Checks (Off)

This fixes a bogus style check failure for long lines in rare cases
where the compiler is invoked, with a -gnatyX switch where X is neither
'm' nor 'M', on a unit which contains "with" clauses for other units
that contain a pragma Style_Checks (Off).

2019-08-13  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	* sem.adb (Do_Analyze): Recompute Style_Check_Max_Line_Length
	after restoring Style_Max_Line_Length.

From-SVN: r274352