replace quoted:from_url with cowboy_http:urldecode

This change makes the dependency on quoted optional
by adding a minimal urldecode function to cowboy.

A protocol option for setting the urldecoding function
has been added to the cowboy_http_protocol module.
The default value for this option is set to be
equivalent to the default settings for quoted.

{fun cowboy_http:urldecode/2, crash}

A note has been added in the README to document
how to use quoted instead of this function.

A field to store this option value has been added
to the state record in the cowboy_http_protocol
module and the http_req record in include/http.hrl

Functions that previously used quoted:from_url/1
has been updated to require an equivalent function
in addition to the previously required arguments.

This change removes a C compiler from the build
requirements of cowboy. It also removes the requirement
to cross compile the code if the target arch/OS
is different from the arch/OS used to build it.

include/http.hrl

@@ -68,5 +68,8 @@
 	%% Response.
 	resp_state = waiting   :: locked | waiting | chunks | done,
 	resp_headers = []      :: http_headers(),
-	resp_body  = <<>>      :: binary()
+	resp_body  = <<>>      :: binary(),
+
+	%% Functions.
+	urldecode :: {fun((binary(), T) -> binary()), T}
 }).