curl: 7.36.0 -> 7.38.0

curl: 7.36.0 -> 7.38.0

Main changes:
- URL parser: IPv6 zone identifiers are now supported
- cyassl: Use error-ssl.h when available (drop local patch)
- polarssl: support CURLOPT_CAPATH / --capath
- mkhelp: generate code for --disable-manual as well (drop local patch)

Full release notes: http://curl.haxx.se/changes.html

MIPS 34kc binary size:
- 7.36.0 before: 82,539 bytes
- 7.38.0 after: 83,321 bytes

Signed-off-by: Catalin Patulea <cat@vv.carleton.ca>
Backport of r42517

git-svn-id: svn://svn.openwrt.org/openwrt/branches/barrier_breaker@42612 3c298f89-4303-0410-b956-a3cf2f4a3e73