Memory size, mask and function table size are 32-bit values in wasm.
There is no relation to pointer size. Hence, replace uintptr_t by
uint32_t.
These fields are already being loaded as uint32_t in wasm-compiler.cc,
causing problems on big endian systems.

R=mstarzinger@chromium.org

Change-Id: Ie03b552934262d5fa8de9998abdd7409e60af690
Reviewed-on: https://chromium-review.googlesource.com/1005154
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Cr-Commit-Position: refs/heads/master@{#52568}