%extend for nested unnamed C structs
test added for nested unnamed C struct %extend
global unnamed structures ignored
obscure case workaround in std::set wrapper, where ignored type still need to be processed
Merge branch 'wkalinin-csymbols-1'

* wkalinin-csymbols-1:
  obscure case workaround in std::set wrapper, where ignored type still need to be processed
  global unnamed structures ignored
  test added for nested unnamed C struct %extend
  %extend for nested unnamed C structs
Create separate extetnd.c file for handling extensions / %extend

This is just a simple code refactor, moving and function renaming to
remove the %extend code out of the parser into its own file now
 that it isn't just used in the parser.
Add missing entries into changes files.