Build when PAHO_USE_SELECT=TRUE is broken in 1.3.16

[smallSwed]

Describe the bug
When building with USE_SELECT defined the compilation fails because of several issues.

• New function introduced in 1.3.16 use members of the Sockets which are only present when the USE_SELECT is not defined. The function: int isConnectPending(int index)
• error: conflicting types for ‘Socket_getReadySocket’ the USE_SELECT version of this function missing the interrupted parameter.
• ...

To Reproduce
Take a library trace as outlined in the README, and/or have a program or describe the steps to reproduce the behavior:

1. generate cmake with -DPAHO_USE_SELECT=TRUE
2. build project with cmake --build .
3. See build errors

Expected behavior
The using PAHO_USE_SELECT=TRUE still builds successfully and usable

Build output

sok@C-W-SOK /tmp/build.paho$ cmake -DPAHO_WITH_SSL=TRUE -DPAHO_BUILD_DOCUMENTATION=FALSE -DPAHO_BUILD_SAMPLES=TRUE -DPAHO_USE_SELECT=TRUE ~/work/git/paho.mqtt.c
-- CMake version: 3.28.3
-- CMake system name: Linux
-- Timestamp is 2026-08-12T12:09:08Z
-- Using OpenSSL with headers at /usr/include
-- Configuring done (0.0s)
-- Generating done (0.0s)
-- Build files have been written to: /tmp/build.paho
sok@C-W-SOK /tmp/build.paho$ cmake --build .
[  1%] Building C object src/CMakeFiles/common_obj.dir/MQTTTime.c.o
[  2%] Building C object src/CMakeFiles/common_obj.dir/MQTTProtocolClient.c.o
[  3%] Building C object src/CMakeFiles/common_obj.dir/Clients.c.o
[  3%] Building C object src/CMakeFiles/common_obj.dir/utf-8.c.o
[  4%] Building C object src/CMakeFiles/common_obj.dir/MQTTPacket.c.o
[  5%] Building C object src/CMakeFiles/common_obj.dir/MQTTPacketOut.c.o
[  6%] Building C object src/CMakeFiles/common_obj.dir/Messages.c.o
[  6%] Building C object src/CMakeFiles/common_obj.dir/Tree.c.o
[  7%] Building C object src/CMakeFiles/common_obj.dir/Socket.c.o
/home/sok/work/git/paho.mqtt.c/src/Socket.c: In function ‘isConnectPending’:
/home/sok/work/git/paho.mqtt.c/src/Socket.c:578:32: error: ‘Sockets’ has no member named ‘saved’
  578 |         SOCKET* socket = &mod_s.saved.fds_write[index].fd;
      |                                ^
/home/sok/work/git/paho.mqtt.c/src/Socket.c:583:40: error: ‘Sockets’ has no member named ‘saved’
  583 |                         *socket, (mod_s.saved.fds_write[index].revents & POLLOUT));
      |                                        ^
/home/sok/work/git/paho.mqtt.c/src/Socket.c: At top level:
/home/sok/work/git/paho.mqtt.c/src/Socket.c:600:8: error: conflicting types for ‘Socket_getReadySocket’; have ‘int(int,  int,  pthread_mutex_t *, int *)’
  600 | SOCKET Socket_getReadySocket(int more_work, int timeout, mutex_type mutex, int* rc)
      |        ^~~~~~~~~~~~~~~~~~~~~
In file included from /home/sok/work/git/paho.mqtt.c/src/Socket.c:35:
/home/sok/work/git/paho.mqtt.c/src/Socket.h:144:8: note: previous declaration of ‘Socket_getReadySocket’ with type ‘int(int,  int,  pthread_mutex_t *, int *, int *)’
  144 | SOCKET Socket_getReadySocket(int more_work, int timeout, mutex_type mutex, int* rc, int* interrupted);
      |        ^~~~~~~~~~~~~~~~~~~~~
gmake[2]: *** [src/CMakeFiles/common_obj.dir/build.make:188: src/CMakeFiles/common_obj.dir/Socket.c.o] Error 1
gmake[1]: *** [CMakeFiles/Makefile2:202: src/CMakeFiles/common_obj.dir/all] Error 2
gmake: *** [Makefile:166: all] Error 2

Environment (please complete the following information):

• OS: Ubuntu
• Version 24

[smallSwed]

It also seems that in the Socket.c when the USE_SELECT is defined the Socket_addSocket and Socket_close does not lock the socket_mutex, while the non-USE_SELECT version does lock it