[Ada] Spurious size error on fixed point type with aspect Small

[Ada] Spurious size error on fixed point type with aspect Small

This path fixes a spurious size error on a fixed point that carries an
aspect specification for the 'Small of the type, when there is a subsequent
derivation of that type before the type is frozen, the given 'Small is not
not a power of two, and the bounds of the type require its full size, also
given by an aspect specification.

2018-05-22  Ed Schonberg  <schonberg@adacore.com>

gcc/ada/

	* freeze.adb (Freeze_Fixed_Point_Type): If the first subtype has
	delayed aspects, analyze them now, os that the representation of the
	type (size, bounds) can be computed and validated.

gcc/testsuite/

	* gnat.dg/fixedpnt3.adb: New testcase.

From-SVN: r260511