gdb/testsuite/gdb.dwarf2: Replace @ with % for ARM compatability.

The ARM assembler recognises @ symbol as a comment marker and
therefore is unable to assemble some of gdb.dwarf2 testsuite tests.
This patch replaces all occurrences of @ symbol with % sign to allow
tests stay compatible with both ARM and x86 assembly. This patch has
been tested on x86_64 and ARMv7 targets.

gdb/testsuite/ChangeLog:

2013-07-19  Omair Javaid  <Omair.Javaid@linaro.org>

        * gdb.dwarf2/fission-reread.S: Replace @ sign with % sign to remove
        assembler errors on arm.
        * gdb.dwarf2/mac-fileno.S: Likewise.
        * gdb.dwarf2/member-ptr-forwardref.S: Likewise.
        * gdb.dwarf2/pr13961.S: Likewise.
gdb/testsuite/gdb.base: Enable disp-step-syscall.exp tests for ARM.

disp-step-syscall.exp is not run for ARM targets because ARM syscall
instructions have not been added to the list of possible syscall
instructions. This patch adds ARM syscall instructions to enable
disp-step-syscall.exp tests for ARM targets. Attached patch is tested
on ARMv7 and helps pass all disp-step-syscall.exp tests for ARM
targets.

gdb/testsuite/ChangeLog:

2013-07-19  Omair Javaid  <Omair.Javaid@linaro.org>

	* gdb.base/disp-step-syscall.exp: Add svc and swi syscall
	instructions and enable disp-step-syscall for arm targets.
	* ldgram.y: Add ALIGN_WITH_INPUT output section attribute.
	* ldlang.c: Likewise.
	* ldlang.h: Likewise.
	* ldlex.l: Likewise.
	* mri.c: Likewise.
	* ld.texinfo: Document new feature.
	* NEWS: Mention new feature.

	* ld-scripts/script.exp: Run align with input test.
	* ld-scripts/align-with-input.t: New file.
	* ld-scripts/rgn-at8.d: Likewise.
	* ld-scripts/rgn-at8.t: Likewise.
	PR binutils/15745
	* readelf.c (get_unwind_section_word): Whilst searching for a
	reloc section associated with an unwind section, check the type as
	well as the section number.