win vs2015: avoid some variable shadowing warnings in crypto/p224

win vs2015: avoid some variable shadowing warnings in crypto/p224

e.g.

d:\src\cr2\src\crypto\p224.cc(478): error C2220: warning treated as error - no 'object' file generated
d:\src\cr2\src\crypto\p224.cc(478): warning C4456: declaration of 'j' hides previous local declaration
d:\src\cr2\src\crypto\p224.cc(447): note: see declaration of 'j'
d:\src\cr2\src\crypto\p224.cc(498): warning C4456: declaration of 'i' hides previous local declaration
d:\src\cr2\src\crypto\p224.cc(447): note: see declaration of 'i'
d:\src\cr2\src\crypto\p224.cc(516): warning C4456: declaration of 'i' hides previous local declaration
d:\src\cr2\src\crypto\p224.cc(447): note: see declaration of 'i'
d:\src\cr2\src\crypto\p224.cc(526): warning C4456: declaration of 'i' hides previous local declaration
d:\src\cr2\src\crypto\p224.cc(447): note: see declaration of 'i'
d:\src\cr2\src\crypto\p224.cc(694): warning C4458: declaration of 'x' hides class member
d:\src\cr2\src\crypto\p224.h(35): note: see declaration of 'crypto::p224::Point::x'
d:\src\cr2\src\crypto\p224.cc(694): warning C4458: declaration of 'y' hides class member
d:\src\cr2\src\crypto\p224.h(35): note: see declaration of 'crypto::p224::Point::y'

R=rsleevi@chromium.org
BUG=440500
Committed: https://crrev.com/cb6a123e432e617052721ef43823fd60b002284e
Cr-Commit-Position: refs/heads/master@{#317398}

[Ryan Sleevi, 2015-02-20 20:00:18]

lgtm

[scottmg, 2015-02-20 20:24:38]

The CQ bit was checked by scottmg@chromium.org

[commit-bot: I haz the power, 2015-02-20 20:25:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/945633003/1

[commit-bot: I haz the power, 2015-02-20 20:59:41]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-20 21:00:30]

Patchset 1 (id:??) landed as
https://crrev.com/cb6a123e432e617052721ef43823fd60b002284e
Cr-Commit-Position: refs/heads/master@{#317398}