Tweak the increase in size of the destination buffer when needed
Tweak the increase in size of the destination buffer when needed

The previous increase was exponentially increasing, which is
unecessarily large. Instead estimate it from the unread source
bytes witha suitable multiplication.

Comparing with previous increase:

$ python -m timeit -r 10 -s 'import lz4.frame as f; raw = open("t.lz4").read()' -- 'len(f.decompress(raw))'

where `t.lz4` being is file with compressed data from
test_compress_huge_with_size shows no increase in time taken

python-lz4/python-lz4,python-lz4/python-lz4