Allow nested function displays

Allow nested function displays

In Ada, it's possible to have nested functions.  However,
block.c:contained_in does not recognize this.  Normally, this is no
problem, but if gdb is stopped inside a nested function, then you can
end up in the unexpected situation that "print" of an expression will
work, whereas "display" of the same expression will not -- because
contained_in returns 0.

This patch simply removes the BLOCK_FUNCTION check from contained_in.
The rationale here is that in languages without nested functions, this
will not cause any issues.

gdb/ChangeLog
2019-07-30  Tom Tromey  <tromey@adacore.com>

	* block.c (contained_in): Remove BLOCK_FUNCTION check.

gdb/testsuite/ChangeLog
2019-07-30  Tom Tromey  <tromey@adacore.com>

	* gdb.ada/display_nested.exp: New file.
	* gdb.ada/display_nested/foo.adb: New file.
	* gdb.ada/display_nested/pack.adb: New file.
	* gdb.ada/display_nested/pack.ads: New file.