[Buffer] Unable to create buffer with max value of unsigned long

[xiaolongx]

We test test-buffer.js, fail to create buffer with unsigned long value(2^32-1)
We find the buffer only accept the max unsigned long value smaller than 257, but the range is 0~4294967295

Commid id	Date	Result
c21b9fe	Sep 23	Pass
147bb63	Oct 7	Fail

Log info:
FAIL - The length of Buffer(4294967295) expected:4294967295 got:undefined
zjs_buffer_create: unable to allocate buffer
FAIL - The length of Buffer(4294967296) expected:4294967295 got:undefined

[grgustaf]

Obviously it was never going to work to have a 4GB buffer on a machine with 80KB of RAM. :)

Someone should dig into how exactly this got limited to 256 so we understand and document it, at least.

[xiaolongx]

This issue cannot reproduce with commit a162db1 on both Arduino_101