Define DIFF_EXPR_OK for avr target to allow PC relative difference relocation.

Define DIFF_EXPR_OK for avr target to allow PC relative difference relocation.

When generating relocation (tc_gen_reloc) 32 bit relocation fixup
is changed to new 32 bit PC relative relocation if the fixup has pc-relative
flag set.

bfd/ChangeLog

2015-07-06  Pitchumani Sivanupandi <pitchumani.s@atmel.com>

    * elf32-avr.c: Add 32 bit PC relative relocation for AVR target.

gas/ChangeLog

2015-07-06  Pitchumani Sivanupandi <pitchumani.s@atmel.com>

    * config/tc-avr.c (tc_gen_reloc): Change 32 bit relocation to
    32 bit PC relative and update offset if the fixup is pc-relative.
    * config/tc-avr.h (DIFF_EXPR_OK): Define to enable PC relative diff
    relocs.

gas/testsuite/ChangeLog

2015-07-06  Pitchumani Sivanupandi <pitchumani.s@atmel.com>

    * gas/avr/pc-relative-reloc.d: New test for 32 bit pc relative reloc.
    * gas/avr/per-function-debugline.s: New test source.

include/ChangeLog

2015-07-06  Pitchumani Sivanupandi <pitchumani.s@atmel.com>

    * elf/avr.h: Add new 32 bit PC relative relocation.

ld/testsuite/ChangeLog

2015-07-06  Pitchumani Sivanupandi <pitchumani.s@atmel.com>

    * ld-avr/gc-section-debugline.d: New test.
    * ld-avr/per-function-debugline.s: Source for new test.