Fix a bug in format localized number on s390x

[samding01]

When building Foundation test on s390x, there is a warning:

   CoreFoundation/String.subproj/CFString.c:6030:36: warning: result of comparison of constant -1 with expression of type 'char' is always false [-Wtautological-constant-out-of-range-compare]

The debugging shows (disableLocalizedFormatting == -1) is never true because disableLocalizedFormatting is defined as char, and then the logic of format localized number is not correct on s390x.

Changing disableLocalizedFormatting to short to make the logic works on all platforms

[spevans]

@swift-ci test

[compnerd]

@samding01 ... I assume that is due to the use of -funsigned-char. I think that the better thing to do here might be to pass in -fsigned-char to the CoreFoundation build, since it does make that assumption in a bunch of places. Alternatively, use _Bool rather than changing this to a short.

[spevans]

Doesn't it need to hold one of 3 values though, so _Bool wouldn't be sufficient? Or maybe just make it an int?

[samding01]

Thanks @compnerd and @spevans Updated to int

[spevans]

@swift-ci test

[samding01]

Can you review and test?

[compnerd]

@swift-ci please test and merge