make static C and C.UTF-8 locales available outside of newlocale

implement fail-safe static locales for newlocale

this frees applications which need to make temporary use of the C
locale (via uselocale) from the possibility that newlocale might fail.

the C.UTF-8 locale is also provided as a static locale. presently they
behave the same, but this may change in the future.

rename internal locale file handling locale maps

since the __setlocalecat function was removed, the filename
__setlocalecat.c no longer made sense.