apply: avoid fixed-size buffer in create_one_file()

apply: avoid fixed-size buffer in create_one_file()

PATH_MAX is not always a hard limit and 'path' in create_one_file()
could be longer -- it's taken from the patch file and allocated
dynamically.  Allocate the name of the temporary file on the heap as
well instead of using a fixed-size buffer to avoid that arbitrary limit.

Resist the temptation of using the more convenient mkpath() to avoid
introducing a dependency on a static variable deep inside the apply
machinery.

Take care to work around (arguably buggy) implementations of free(3)
that modify errno, by calling it only after using the errno value.

Suggested-by: Jeff King <peff@peff.net>
Helped-by: Jeff King <peff@peff.net>
Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>