Fix warning in PoolAlloc.cpp.

Use "I" instead of "l" as printf type prefix for size_t.
Review URL: https://codereview.appspot.com/5572071

git-svn-id: https://angleproject.googlecode.com/svn/trunk@966 736b8ea6-26fd-11df-bfd4-992fa37f6226
1 file changed