builtin/config.c: compilation fix

Do not feed a random string as the first parameter to die(); use "%s"
as the format string instead.

Do the same for test-urlmatch-normalization.c while saving a single
pointer variable by turning a "const char *" constant string into
"const char []", which is sufficient to squelch compilation warning
(the compiler can see usage[] given to die() is a constant and will
never have conversion specifiers that cause trouble).  But for a
good measure, give them the same "%s" treatment as well.

Signed-off-by: Junio C Hamano <gitster@pobox.com>