argv: do fewer memory re-allocations

argv: do fewer memory re-allocations

Prevent the re-allocations of memory when the internal argv grows
beyond 2 and 4 arguments by initially allocating argv to hold up to
7 (+ trailing NULL) pointers.

While at it rename argv_reset to argv_free to actually express
what's going on. Redo the argv_reset functionality so that it can
be used to actually reset the argv without re-allocation.

Signed-off-by: Heiko Hund <heiko.hund@sophos.com>
Signed-off-by: David Sommerseth <davids@openvpn.net>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <20200206132103.15977-3-davids@openvpn.net>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg19378.html