Show optimized out local variables in "info locals"

Show optimized out local variables in "info locals"

Currently, optimized out variables are not shown when doing "info
locals".  Some users found that confusing, thinking GDB forgot to print
their variable.  This patch adds them to the "info locals" output.  I
added a test in gdb.dwarf2 to test for that behavior.  I think doing a
synthetic DWARF test is the easiest way to have an optimized out local
variable for sure.

However, this change reveals what I think is a bug in GDB, see:

http://lists.dwarfstd.org/pipermail/dwarf-discuss-dwarfstd.org/2017-September/004394.html

This patch marks the tests in inline-locals.exp that start failing as
KFAIL.  I'd like to tackle this bug eventually, but I don't have the
time right now.  I think it's still better to show an extra erroneous
entry than to not show the optimized out variables at all.  I haven't
created a bug in bugzilla yet, but if we agree it's indeed a bug,  I'll
create one and update the setup_kfail lines with the actual bug number
before pushing.

gdb/ChangeLog:

	* stack.c (iterate_over_block_locals): Add LOC_OPTIMIZED_OUT
	case in switch.

gdb/testsuite/ChangeLog:

	* gdb.opt/inline-locals.exp: Mark tests as KFAIL.
	* gdb.dwarf2/info-locals-optimized-out.exp: New file.
	* gdb.dwarf2/info-locals-optimized-out.c: New file.