[Ada] Fix alignment of mutex_t and cond_t type on 32-bit SPARC/Solaris

[Ada] Fix alignment of mutex_t and cond_t type on 32-bit SPARC/Solaris

The alignment of the couple of types from System.OS_Interface was wrongly
set to 4 (32-bit) instead of 8 (64-bit) in 32-bit mode.

2018-07-31  Eric Botcazou  <ebotcazou@adacore.com>

gcc/ada/

	*  libgnarl/s-osinte__solaris.ads (upad64_t): New private type.
	(mutex_t): Use it for 'lock' and 'data' components.
	(cond_t): Likewise for 'data' and use single 'flags' component.

From-SVN: r263099