fix: Parse negative ASCII integer values correctly

[pranavmangal]

The geocoding API was returning positive elevation values for places below sea level (e.g: Jericho with elevation -233m).

The issue seems to be the custom ASCII parsing:

In asciiToInt8, asciiToInt16 and asciiToInt32, the minus character (-, ASCII 45) was handled via ret = ret * -1. Because since ret is initialized to 0, when a leading - is encountered, 0 * -1 = 0, causing the negative sign to be lost during parsing.

Fixes #38

[terraputix]

Hi @pranavmangal, thanks for investigating and fixing this issue, looks fine from my side!
As these changes require the db to be rebuilt and as we are working on some related improvements, it will not be deployed right away and it might take a couple of days until these changes are live on geocoding-api.open-meteo.com.