Add methods for returning the ports civetweb is listening on

Patch civetweb to provide a method for retrieving the listening ports.

* Verified builds for:
   * MacOS X 10.8 - Xcode 5
   * MS Visual Studio 2012 Express on Windows 7
ANSI <= C-90 compliance - for loop init

* Move var declaration outside of for loop initialization
Use size_t when iterating over port and ssl vars in mg_get_ports

* Parameter passed in indicating size of port and ssl arrays passed
  in is size_t - an unsigned var, make sure to use the same type
  for the iteration variable.
Fix sign comparison warning in mg_get_ports

ctx->num_listening_sockets is a signed int. i is a size_t (unsigned long).
mg_get_ports to return number of elements of ports and ssl filled in

* Return the number of elements of the ports and ssl arrays passed in,
  so that the caller knows how many ports the server is listening on/
  how many elements of ports/ssl are valid.
Merge pull request #34 from keithel/getports

Add methods for returning the ports civetweb is listening on