native: Fix utime() for windows

Apparently the units are in milliseconds, not in seconds!
Rename guessing_game.rs to main.rs in guide
docs: Fix typo in tutorial.
doc: Fix the 30-minute intro to use += operator.

The 30-minute intro had a comment mentioning that `+=` will be included in the future. It's already included, and this fixes it to use `+=`.
Fixes missing overflow lint for i64 #14269

The `type_overflow` lint, doesn't catch the overflow for `i64` because
the overflow happens earlier in the parse phase when the `u64` as biggest
possible int gets casted to `i64` , without checking the for overflows.
We can't lint in the parse phase, so a refactoring of the `LitInt` type
was necessary.

The types `LitInt`, `LitUint` and `LitIntUnsuffixed` where merged to one
type `LitInt` which stores it's value as `u64`. An additional parameter was
added which indicate the signedness of the type and the sign of the value.
auto merge of #16234 : cakebaker/rust/rename_guessing_game_rs_to_main_rs, r=steveklabnik

Follow-up to #16215
auto merge of #16243 : alexcrichton/rust/fix-utime-for-windows, r=brson

Apparently the units are in milliseconds, not in seconds!
auto merge of #16246 : ruud-v-a/rust/patch-1, r=brson
auto merge of #15709 : hirschenberger/rust/issue-14269, r=cmr

Fixes missing overflow lint for i64 #14269

The `type_overflow` lint, doesn't catch the overflow for `i64` because the overflow happens earlier in the parse phase when the `u64` as biggest possible int gets casted to `i64` , without checking the for
overflows.
We can't lint in the parse phase, so we emit a compiler error, as we do for overflowing `u64`

Perhaps a consistent behaviour would be to emit a parse error for *all*  overflowing integer types.

See #14269
auto merge of #16247 : TimDumol/rust/patch-1, r=alexcrichton

The 30-minute intro had a comment mentioning that `+=` will be included in the future. It's already included, and this fixes it to use `+=`.
Turn off segmented stack support and use stack probes instead

Fixes #10781, #11359, #13259, #14742 and #16012.
Killing off segmented stack code.