rts: fix I/O manager compilation errors for win32 target

This patch fixes I/O manager compilation errors for win32 target
discovered when cross-compiling to win32 using recent clang:

```
rts/win32/ThrIOManager.c:117:7: error:
     error: call to undeclared function 'is_io_mng_native_p'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
      117 |   if (is_io_mng_native_p ()) {
          |       ^
    |
117 |   if (is_io_mng_native_p ()) {
    |       ^

1 error generated.
`x86_64-w64-mingw32-clang' failed in phase `C Compiler'. (Exit code: 1)

rts/fs.c:143:28: error:
     error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]
      143 | int setErrNoFromWin32Error () {
          |                            ^
          |                             void
    |
143 | int setErrNoFromWin32Error () {
    |                            ^

1 error generated.
`x86_64-w64-mingw32-clang' failed in phase `C Compiler'. (Exit code: 1)

rts/win32/ConsoleHandler.c:227:9: error:
     error: call to undeclared function 'interruptIOManagerEvent'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
      227 |         interruptIOManagerEvent ();
          |         ^
    |
227 |         interruptIOManagerEvent ();
    |         ^

rts/win32/ConsoleHandler.c:227:9: error:
     note: did you mean 'getIOManagerEvent'?
    |
227 |         interruptIOManagerEvent ();
    |         ^

rts/include/rts/IOInterface.h:27:10: error:
     note: 'getIOManagerEvent' declared here
       27 | void *   getIOManagerEvent  (void);
          |          ^
   |
27 | void *   getIOManagerEvent  (void);
   |          ^

1 error generated.
`x86_64-w64-mingw32-clang' failed in phase `C Compiler'. (Exit code: 1)

rts/win32/ConsoleHandler.c:196:9: error:
     error: call to undeclared function 'setThreadLabel'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
      196 |         setThreadLabel(cap, t, "signal handler thread");
          |         ^
    |
196 |         setThreadLabel(cap, t, "signal handler thread");
    |         ^

rts/win32/ConsoleHandler.c:196:9: error:
     note: did you mean 'postThreadLabel'?
    |
196 |         setThreadLabel(cap, t, "signal handler thread");
    |         ^

rts/eventlog/EventLog.h:118:6: error:
     note: 'postThreadLabel' declared here
      118 | void postThreadLabel(Capability    *cap,
          |      ^
    |
118 | void postThreadLabel(Capability    *cap,
    |      ^

1 error generated.
`x86_64-w64-mingw32-clang' failed in phase `C Compiler'. (Exit code: 1)
```

(cherry picked from commit 710665bd)
(cherry picked from commit 9499ed96)