bf_read::ReadSignedVarInt64 Incorrect intermediate type

[SizzlingCalamari]

https://github.com/ValveSoftware/source-sdk-2013/blob/master/src/tier1/bitbuf.cpp#L1067

In bf_read::ReadSignedVarInt64, the encoded value is read into a uint32, which should be a uint64. This looks like a copy paste bug.

Current:

int64 bf_read::ReadSignedVarInt64()
{
    uint32 value = ReadVarInt64();
    return bitbuf::ZigZagDecode64( value );
}

Fixed:

int64 bf_read::ReadSignedVarInt64()
{
    uint64 value = ReadVarInt64();
    return bitbuf::ZigZagDecode64( value );
}

[SizzlingCalamari]

still an issue

[AdamTadeusz]

For what it's worth I did a small test here when extending m_nButtons to uint64 and the fix worked for the one test case I checked, although ended up using WriteLongLong in the end anyway