bugfix: use of LuaJIT FFI when disabling the Lua code cache would lead to LuaJIT GC assertion failures like "g->gc.total == sizeof(GG_State)" because we unloaded the standard "ffi" module. thanks Ron Gomes for reporting this issue.
Revert "bugfix: use of LuaJIT FFI when disabling the Lua code cache would lead to LuaJIT GC assertion failures like "g->gc.total == sizeof(GG_State)" because we unloaded the standard "ffi" module. thanks Ron Gomes for reporting this issue."

Preventing unloading "ffi" does not reallys solve the issue here because
we can end up with FFI ctype redefinition errors.

This reverts commit b3218be26612282109897651ed5ccd4ab18a9e06.
tests: replaced the domain name "direct.agentzh.org" with "agentzh.org".
fixed failing test cases to reflect the multi-value header change in nginx 1.4.1.
updated .gitignore a bit.
change: made ngx.say/ngx.print/ngx.eof/ngx.flush/ngx.send_headers return nil and a string describing the error in case of most of the common errors (instead of throwing out an exception), and return 1 for success.
bugfix: ngx.flush(true) might not return 1 on success.
updated docs to reflect recent changes.
Merge branch 'master' into ffi
optimize: avoided use of the nginx request objects in ngx.escape_uri, ngx.unescape_uri, ngx.quote_sql_str, ngx.decode_base64, ngx.encode_base64, and ngx.decode_args.
optimize: avoided use of the nginx request objects in ngx.encode_args.
updated README.markdown to reflect recent changes in docs.
refactor: added inline functions ngx_http_lua_get_req and ngx_http_lua_set_req to eliminate code duplication when storing or fetching the nginx request object from the lua global variable table.
refactor: no longer store cf->log into the lua registry table because we can directly access the global ngx_cycle->log thing.
Merge branch 'master' into ffi
bugfix: t::TestNginxLua: env TEST_NGINX_INIT_BY_LUA would break existing init_by_lua_file directive in the test case.
refactor: now we store the nginx request object as a named Lua global variable __ngx_req to help FFI-based Lua code access it.
Merge remote-tracking branch 'origin/master' into ffi
feature: added pure C API for ngx.exit, which is expected to be used with LuaJIT FFI (or lua-resty-core in particular). also added coroutine._yield for the original std version of coroutine.yield.