Fix: allow input of numbers greater than INT32_MAX for GiveMoney (#8499)

Based on patch by JGR.

src/main_gui.cpp

@@ -73,7 +73,7 @@ void HandleOnEditText(const char *str)
 		case 3: { // Give money, you can only give money in excess of loan
 			const Company *c = Company::GetIfValid(_local_company);
 			if (c == nullptr) break;
-			Money money = min(c->money - c->current_loan, (Money)(atoi(str) / _currency->rate));
+			Money money = min(c->money - c->current_loan, (Money)(strtoull(str, nullptr, 10) / _currency->rate));
 
 			uint32 money_c = Clamp(ClampToI32(money), 0, 20000000); // Clamp between 20 million and 0