bitsPerValue test: restrict max value to 31 on linux 32 bit

[mtasaka]

NOTE: Mark this as "Draft" because this depends on #63 and #60

On grib_bitsPerValue.sh, restrict maximum bitsPerValue value (MAX_BPV) to 31 on linux 32 bit, higher value is not supported.

Note that currently on Windows system, MAX_BPV is set to 26 instead of 31, but this should be able to be changed to 31 as well on Windows as this should be fixed with "decode_long_array: avoid overflow on 32 bit when overread" change.

Also, on linux 64 bit system, change MAX_BPV to 63. This should also be fixed with the above change.

The proposal patch fixes the following test failure on Linux 32 #bit:

# 153 - eccodes_t_grib_bitsPerValue

Exported from https://jira.ecmwf.int/browse/SUP-3563

[mtasaka]

https://ci.appveyor.com/project/ecmwf/eccodes/builds/42144907 says Windows build does not pass tests with this change: This is (currently) expected because as said above, this change needs #60 beforehand.

[shahramn]

OK. Thanks for the explanation

[shahramn]

We no longer support 32bit platforms