sdr: Fix segfault on invalid unit types

[AlexanderAmelkin]

The program would crash if the BMC returned an out of range (>90)
unit type for a full sensor record. This commit adds a range check
and also add support for IPMI 2.0 additional unit types 91 and 92
("fatal error" and "grams").

Resolves #118

Signed-off-by: Alexander Amelkin alexander@amelkin.msk.ru

[leye7755]

#118 At present, I simply set the value beyond this range to 0.

[AlexanderAmelkin]

@leye7755, does THIS patch work for you? Please build from this branch and tell me if it works:

# (assuming you're inside the cloned repo)
git checkout bugfix/118-fix-sdr-unit-segfault
./bootstrap
./configure
make