Fix get_tool_wear_after_use for one use (insta-break)

[grorp]

minetest/doc/lua_api.txt

Lines 3683 to 3688 in 6191baf

	* `minetest.get_tool_wear_after_use(uses [, initial_wear])`
	* Simulates a tool being used once and returns the added wear,
	such that, if only this function is used to calculate wear,
	the tool will break exactly after `uses` times of uses
	* `uses`: Number of times the tool can be used
	* `initial_wear`: The initial wear the tool starts with (default: 0)

Currently minetest.get_tool_wear_after_use(1, 0) (tool should break after 1 use and doesn't have any wear yet) returns 0. Actually it should return 65536 in order to instantly break the tool. The wrong return value is caused by ModApiUtil::l_get_tool_wear_after_use incorrectly casting the return value of calculateResultWear from u32 to u16. This PR fixes that.

• Does it resolve any reported issue?
  No, I thought it was small enough not to open an issue.

• If not a bug fix, why is this PR needed? What usecases does it solve?
  It's a bug fix.

To do

This PR is Ready for Review.

How to test

Try minetest.get_tool_wear_after_use(1, 0). It should return 65536.