instancepool: Remove older C prototypes
instancepool: Remove older C prototypes

Unfortunately we overlooked this in the previous commit

Change-Id: I53a55b1db4536e61a67c496f04d024a6cc738714
Reviewed-on: http://review.couchbase.org/39954
Tested-by: Mark Nunberg <e7d42768707bf23038325b0b68d4b577e5f6064a@haskalah.org>
Reviewed-by: Brett Lawson <c8c4369773d7d7226e031f0c4af62e3f38a08510@gmail.com>

couchbase/libcouchbase,avsej/libcouchbase,kojiromike/libcouchbase,kojiromike/libcouchbase,mody/libcouchbase,mnunberg/libcouchbase,kojiromike/libcouchbase,avsej/libcouchbase,couchbase/libcouchbase,PureSwift/libcouchbase,mnunberg/libcouchbase,couchbase/libcouchbase,senthilkumaranb/libcouchbase,mody/libcouchbase,PureSwift/libcouchbase,PureSwift/libcouchbase,mnunberg/libcouchbase,mnunberg/libcouchbase,maxim-ky/libcouchbase,signmotion/libcouchbase,avsej/libcouchbase,senthilkumaranb/libcouchbase,avsej/libcouchbase,avsej/libcouchbase,senthilkumaranb/libcouchbase,couchbase/libcouchbase,signmotion/libcouchbase,maxim-ky/libcouchbase,PureSwift/libcouchbase,couchbase/libcouchbase,kojiromike/libcouchbase,mody/libcouchbase,avsej/libcouchbase,maxim-ky/libcouchbase,maxim-ky/libcouchbase,senthilkumaranb/libcouchbase,couchbase/libcouchbase,mnunberg/libcouchbase,signmotion/libcouchbase,signmotion/libcouchbase,mody/libcouchbase,couchbase/libcouchbase,avsej/libcouchbase