Fix memory corruption in locale string

[simmons]

The wrapper for the ncurses setlocale() function converts the provided locale &str to a C string by creating a std::ffi::CString, then passing its inner pointer on to the ncurses function. This inner pointer outlived the CString's temporary lifetime, so the data it pointed to was undefined when calling setlocale(). The fix is to bind the CString to a variable, thus extending its lifetime.

Most of the time this does not result in bad behavior, but if the memory being referred to by the pointer is overwritten before the call to setlocale(), then a garbage locale string may be used. Unable to find the locale, libc will fall back to a "C" locale, and attempts to print most Unicode characters will result in garbage characters being displayed on the terminal.

I haven't been able to reproduce this with a minimal example program, but in my Cursive-based program I can consistently reproduce this and have confirmed in gdb that the dropped memory becomes overwritten in the above fashion somewhere in core::ptr::real_drop_in_place(). This patch fixes the problem.

[jeaye]

Thank you for the PR and for the explanation! I'll make a new release with this now.