The global was only referenced in the main() function, which passes it
as an argument of the same name to the parse_line() function, leading
to gcc -Wshadow warnings:

makekeys.c: In function ‘parse_line’:
makekeys.c:58:24: warning: declaration of ‘buf’ shadows a global declaration
makekeys.c:54:13: warning: shadowed declaration is here
Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>