liba2i-1.0-rc1 - string-to-numeric library

Pre-release for packagers to try.  Changes:

-  Lower the requirements from groff-1.24 to groff-1.22.4.
-  -D_FORTIFY_SOURCE=2.  (=3 produced the same exact code, BTW.)
-  Move A2I_INTERNAL from CPPFLAGS to the .c files.  This makes it less
   brittle.

README: We have a dir for tarballs at <kernel.org>

Signed-off-by: Alejandro Colomar <alx@kernel.org>