[Ada] Unbounded strings: inline Initialize and Adjust

[Ada] Unbounded strings: inline Initialize and Adjust

Procedures Initialize and Adjust in the Ada.[Wide_[Wide_]]Strings.Unbounded
package are now inlined for nondispatching calls. No test available (efficiency
issue only).

2018-05-25  Bob Duff  <duff@adacore.com>

gcc/ada/

	* libgnat/a-strunb__shared.ads, libgnat/a-stwiun__shared.ads,
	libgnat/a-stzunb__shared.ads: (Initialize, Adjust): Add pragma Inline.

From-SVN: r260719