dropbear: update to 2014.63

Upstream changelog:
https://matt.ucc.asn.au/dropbear/CHANGES

This adds elliptic curve cryptography (ECC) support as an option, disabled
by default.

dropbear mips 34kc uClibc binary size:
before: 161,672 bytes
after, without ECC (default): 164,968
after, with ECC: 198,008

Signed-off-by: Catalin Patulea <cat@vv.carleton.ca>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@40297 3c298f89-4303-0410-b956-a3cf2f4a3e73