ada: Add Codepeer Exemption + simplify TO_C code.

ada: Add Codepeer Exemption + simplify TO_C code.

This patch simplify the TO_C code to have a single branch for
raising exception. Furthermore, adding pragma annotate for codepeer
to ignore uninitialized value since this is caused because we have
input check before the initialization.

gcc/ada/

	* libgnat/i-c.adb (To_C): Simplify code for having a single
	exception raise. Add pragma annotate about uninitialized value
	which happen only on exception raising.