[zmq] Call va_end() on va_start()ed args. #10056

A function that invokes va_start, shall also invoke va_end before it returns. (http://www.cplusplus.com/reference/cstdarg/va_start/)

If there is no corresponding call to va_start or va_copy, or if va_end is not called before a function that calls va_start or va_copy returns, the behavior is undefined. http://en.cppreference.com/w/cpp/utility/variadic/va_end

ugh. see this is why we need to test on sparc. :P

(On sparc forgetting to va_end will instantly corrupt the stack.)

utACK, haven't checked though whether this covers all cases.

utACK https://github.com/bitcoin/bitcoin/pull/10056/commits/5ba61f0034597ffeedc8c44af5a6ec670b095d83 @laanwj It covers all returns there.

utACK 5ba61f0034597ffeedc8c44af5a6ec670b095d83. I've check all the usages of va_list (va_start, va_copy) and expect of the ones covered in this PR we are good.

ugh. see this is why we need to test of sparc. :P

That reminds me, ideally we'd use typesafe c++11 variadic templates instead of C varags legacy mess.