1.0.15 only kept a single LINUXTHREADS option, and renamed it, making it
no longer option-compatible with uClibc.
The option for "1.0.14 or later" version of uClibc-ng is not currently
used; rename it to "1.0.15 or later" and use it to handle newer
uClibc-ng's linuxthreads.
m68k happens to be the only sample using linuxthreads.
Signed-off-by: Alexey Neyman <stilor@att.net>