Fix "overflow in PLT unwind data" warning

When linking statically, it's possible to hit this warning with IFUNC
or very large executables, due to .glink being unused.

	* powerpc.cc (do_plt_fde_location): Handle zero length .glink.
	Compare FDE contents with DW_CFA_nop rather than 0.
Fix mi_expect_stop for non-zero exit codes

The message displayed by gdb is different when the inferior exits with
zero and non-zero values, this fix takes that into account.

gdb/testsuite/ChangeLog:
2014-05-13  Simon Marchi  <simon.marchi@ericsson.com>

	* lib/mi-support.exp (mi_expect_stop): Expect message for
	inferiors that exit with non-zero exit code.
Fix argument passing in mi_run_cmd_full

Passing arguments did not work when use_mi_command was set.

gdb/testsuite/ChangeLog:
2014-05-13  Simon Marchi  <simon.marchi@ericsson.com>

	* lib/mi-support.exp (mi_run_cmd_full): Set arguments by calling
	"-exec-arguments" or "set args" before running the inferior.
* dwarf2read.c (read_structure_type): Delete outdated comments.
Make more robust when run in parallel mode.

Since we're not compiling with gcc, we don't know where the
DWO file will ultimately be built.  It could be built in
testsuite/gdb.dwarf2/foo (non-parallel mode) or
testsuite/outputs/gdb.dwarf2/foo (parallel mode).

	* gdb.dwarf2/fission-reread.S: Remove directory from .dwo file path.
	* gdb.dwarf2/fission-reread.exp: Set debug-file-directory before
	loading file.  Add test for TU lookup.
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