Stricter rules when parsing time values to avoid UBSAN error (backport #3148)

[mergify]

This fixes a UBSAN error found by OSS-Fuzz: https://issues.oss-fuzz.com/issues/392928817
The error message is:

/src/exiv2/src/value.cpp:975:43: runtime error: negation of -2147483648 cannot be represented in type 'int'; cast to an unsigned type to negate this value to itself

It happens here:

exiv2/src/value.cpp

Line 975 in 3b58bda

time_.tzMinute = time_.tzHour < 0 ? -minute : minute;

The integer overflow is harmless, but I have fixed it by making the parsing rules stricter.

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This is an automatic backport of pull request #3148 done by Mergify.