liba2i-1.0-rc5 - string-to-numeric library

Pre-release for packagers to try.  Changes since 1.0-rc4:

-  Add 'restrict' where appropriate.
-  Fix portability issues.
-  Always set *endp (NetBSD has changed their specification of strtoi(3)
   to always set it; follow suit).
-  Small source-code readability improvements.

lib/src/: a2i_strto[iu](): Use strcmp(3) instead of byte comparisons

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