doc: added a note about the full-buffering nature of the ngx.location.capture* API. thanks cmaion for the original patch in #607.

Author: agentzh

README.markdown

@@ -3159,7 +3159,7 @@ ngx.location.capture
 
 **context:** *rewrite_by_lua*, access_by_lua*, content_by_lua**
 
-Issue a synchronous but still non-blocking *Nginx Subrequest* using `uri`.
+Issues a synchronous but still non-blocking *Nginx Subrequest* using `uri`.
 
 Nginx's subrequests provide a powerful way to make non-blocking internal requests to other locations configured with disk file directory or *any* other nginx C modules like `ngx_proxy`, `ngx_fastcgi`, `ngx_memc`,
 `ngx_postgres`, `ngx_drizzle`, and even ngx_lua itself and etc etc etc.
@@ -3170,6 +3170,9 @@ Subrequests are completely different from HTTP 301/302 redirection (via [ngx.red
 
 You should always read the request body (by either calling [ngx.req.read_body](#ngxreqread_body) or configuring [lua_need_request_body](#lua_need_request_body) on) before initiating a subrequest.
 
+This API function (as well as [ngx.location.capture_multi](#ngxlocationcapture_multi)) always buffers the whole response body of the subrequest in memory. Thus, you should use [cosockets](#ngxsockettcp)
+and streaming processing instead if you have to handle large subrequest responses.
+
 Here is a basic example:
 
 ```lua

doc/HttpLuaModule.wiki

@@ -2545,7 +2545,7 @@ The <code>ngx.ctx</code> lookup requires relatively expensive metamethod calls a
 
 '''context:''' ''rewrite_by_lua*, access_by_lua*, content_by_lua*''
 
-Issue a synchronous but still non-blocking ''Nginx Subrequest'' using <code>uri</code>.
+Issues a synchronous but still non-blocking ''Nginx Subrequest'' using <code>uri</code>.
 
 Nginx's subrequests provide a powerful way to make non-blocking internal requests to other locations configured with disk file directory or ''any'' other nginx C modules like <code>ngx_proxy</code>, <code>ngx_fastcgi</code>, <code>ngx_memc</code>,
 <code>ngx_postgres</code>, <code>ngx_drizzle</code>, and even ngx_lua itself and etc etc etc.
@@ -2556,6 +2556,9 @@ Subrequests are completely different from HTTP 301/302 redirection (via [[#ngx.r
 
 You should always read the request body (by either calling [[#ngx.req.read_body|ngx.req.read_body]] or configuring [[#lua_need_request_body|lua_need_request_body]] on) before initiating a subrequest.
 
+This API function (as well as [[#ngx.location.capture_multi|ngx.location.capture_multi]]) always buffers the whole response body of the subrequest in memory. Thus, you should use [[#ngx.socket.tcp|cosockets]]
+and streaming processing instead if you have to handle large subrequest responses.
+
 Here is a basic example:
 
 <geshi lang="lua">