Support -g option to dump value string only (no key string, no quotes, no newline).

Added filter for exporting. Also added an export type for exporting value only.

Refined some comments too.

Change-Id: I97fdd408bd444094ccc3378564b37c252fcf213e,
BUG=no bug id
TEST=Compile okay on Z600 and x86-*. Tested on Z600 machine:
vpd -f test  -s ABC=DEF -s DEF=GHI -s IJK=ABC
vpd -f test -l  # all show up
vpd -f test -g abc  # nothing shows up
vpd -f test -g ABC  # DEF is showed.
vpd -f test -l -g  # error check: need an argument for -g
vpd -f test -l -g XXX  # error check: -g and -l must be mutually exclusive.

Review URL:
3 files changed
tree: 1449fa796a77d83b31efed3dbef20dda6bb09398
  1. include/
  2. lib/
  3. util/
  5. Makefile
  7. vpd.c