NaCl: Add the integrated runtime (IRT) library to Windows install images

NaCl: Add the integrated runtime (IRT) library to Windows install images

The dependencies in mini_installer.gyp should be OK, because the
target that produces chrome.exe also copies nacl_irt_* into
<(PRODUCT_DIR) as a side effect.

BUG=http://code.google.com/p/nativeclient/issues/detail?id=1595
TEST=not sure how to test this, apart from manually testing the
  install images that are produced after this is committed

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=84826

[Mark Seaborn, 2011-05-10 11:57:01]

This is split out from http://codereview.chromium.org/6927015/ and extended to
change FILES.

[bradn, 2011-05-10 17:05:56]

LGTM