Increase warning level to 4 on Visual Studio

Increase warning level to 4 on Visual Studio

This requires disabling most /W4 warnings so the patch doesn't get too large.
I still fixed a few bugs so I didn't have to disable some more serious warnings. Most of these warnings are already enabled on gcc so it's mostly windows-specific code that is affected.

BUG=none
TEST=none


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=83840

[nsylvain, 2011-05-02 19:48:54]

LGTM

[commit-bot: I haz the power, 2011-05-03 00:38:16]

Presubmit check for 6902069-2001 failed and returned exit status 1.

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[commit-bot: I haz the power, 2011-05-03 00:48:46]

Presubmit check for 6902069-2001 failed and returned exit status 1.

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** Presubmit ERRORS **
Missing LGTM from an OWNER for: net/third_party/nss/ssl.gyp

[rvargas (doing something else), 2011-05-03 01:04:56]

LGTM

[commit-bot: I haz the power, 2011-05-03 02:04:14]

Change committed as 83840