scripts: objdiff: sync with Linux 3.16

scripts: objdiff: sync with Linux 3.16

Import scripts/objdiff improvements from Linux v3.16, which
consists of 7 commits written by me.

  commit 7fa0e6db3cedc9b70d68a4170f1352e2b1aa0f90
  scripts: objdiff: support directories for the augument of record command

  commit 8ac28bee76eec006aac5ba5c418878a607d53a9b
  scripts: objdiff: fix a comment

  commit 8b5d0f20d64f00ffd5685879f8eb3659379f5aaa
  scripts: objdiff: change the extension of disassembly from .o to .dis

  commit 18165efa8203a34d82f60a1831ea290e7304c654
  scripts: objdiff: improve path flexibility for record command

  commit 1ecc8e489abfdaa6d8d1689f7ff62fdf1adda30c
  scripts: objdiff: remove unnecessary code

  commit 5ab370e91af70d5f1b1dbaec78798a2ff236a2d5
  scripts: objdiff: direct error messages to stderr

  commit fd6e12423311697860f30d10398a0f9eb91977d2
  scripts: objdiff: get the path to .tmp_objdiff more simply

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>