Fix for un-initialized code point variable.

The original CL is http://codereview.chromium.org/5025003/, but it was reverted
because the compiler complains code_point variable is not initialized. This CL
just initializes it.

This CL also adds few lines of code to make code more robust.

Change-Id: Ib1329bcaeb4a1bd9abfe9e766b61bd0e52d2c260

BUG=chromium-os:7542
TEST=RUNTESTS=1 emerge-x86-generic vboot_reference
Manually tested the following commands (intentionally mix Chinese and ASCII):
export C=.../cgpt
export D=/tmp/hda

$C add $D -i 1 -l 批P踢T踢T許C夕C餐
$C find $D -l 批P踢T踢T許C夕C餐
$C show $D
$C add $D -i 1 -l abc012
$C add $D -i 1 -l 是否看過坊間常見的許茹芸淚海慶功宴吃蓋飯第四集
$C add $D -i 1 -l 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ # ok and truncated
$C add $D -i 1 -l `printf "\xf4\x91\x81\x81"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xf4\x8f\xbf\xbf"`
$C add $D -i 1 -l `printf "\xf4\x8f\x44\x44"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xf4\x8f\xbf"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xf0\xbf\xbf\xbf"`
$C add $D -i 1 -l `printf "\xf0\xbf\xbf\x44"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xf0\x80\x80\x80"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xf0\x80\x84\x80"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xf0\x80\x90\x80"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xf0\x88\x80\x80"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xed\x80\x80"`
$C add $D -i 1 -l `printf "\xed\xa0\x80"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xe0\xbf\xbf"`
$C add $D -i 1 -l `printf "\xe0\xbf\x44"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xe0\x80\x80"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xe0\x90\x80"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xe0\xbf"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xd0\x80"`
$C add $D -i 1 -l `printf "\xd0\x11"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xd0"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\xc0\xaf"` # (EXPECT: failed)
$C add $D -i 1 -l `printf "\x80"` # (EXPECT: failed)

Review URL: http://codereview.chromium.org/5104009
4 files changed