You can safely ignore these warnings. You can find out more about this issue by consulting this page: http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dv_vstechart/html/vbtchtroubleshootingnetinteroperability.asp
The "In/Out C-Style Arrays" section is particularly relevant. Bottom-line : if the returned buffer of the specified methods in the warnings were accepting "in" values, you would have to apply the modifications in the article. But since all the listed methods only handle out buffers, the warnings are of no consequence to you nor the framework.
However, if you want to permanently get rid of the warnings (when you do a "Rebuild All" for instance), you will have no choice to proceed as described in the article. You will have to disassemble the interop wrapper (with ildasm), edit the IL and reassemble (with ilasm). This process is also called "creative round tripping".