fix errors reported by SUSE's post-build linter

In StartRFUSocket() in gba/GBALink.cpp move a postincrement out of an
expression to a following statement, because the evaluation order is
undefined.

In GetDevices() in wx/openal.cpp replace an #else with an #endif so that
the function has a default return statement visible to the linter.

In FilterThread::Entry() add a `return 0;` (ExitCode) statement at the
end even though it is probably never reached.

In the TransferToWindow() for the positive double validator widget in
wx/widgets/wxmisc.cpp add a default `return true;`, for the rare case
there is no double value, in which case the string representation would
be displayed (since it is a subclass of wxGenericValidator(wxString&) .)

src/gba/GBALink.cpp

@@ -1918,7 +1918,8 @@ static void StartRFUSocket(uint16_t value)
                                     if (!ok) {
                                         rfu_curclient = rfu_numclients;
                                         rfu_data.rfu_clientidx[(rfu_masterdata[0] - 0x61f1) >> 3] = rfu_numclients;
-                                        rfu_clientlist[rfu_numclients] = rfu_masterdata[0] | (rfu_numclients++ << 16);
+                                        rfu_clientlist[rfu_numclients] = rfu_masterdata[0] | (rfu_numclients << 16);
+                                        rfu_numclients++;
                                         gbaid = (rfu_masterdata[0] - 0x61f1) >> 3;
                                         rfu_data.rfu_signal[gbaid] = 0xffffffff >> ((3 - (rfu_numclients - 1)) << 3);
                                     }

src/wx/openal.cpp

@@ -356,10 +356,10 @@ bool OpenAL::GetDevices(wxArrayString& names, wxArrayString& ids)
         devs += strlen(devs) + 1;
     }
 
-#else
+#endif
+
     // should work anyway, but must always use default driver
     return true;
-#endif
 }
 
 #endif

src/wx/panel.cpp

@@ -1658,6 +1658,8 @@ public:
             done->Post();
             continue;
         }
+
+        return 0;
     }
 };
 

src/wx/widgets/wxmisc.cpp

@@ -393,6 +393,7 @@ bool wxPositiveDoubleValidator::TransferToWindow()
         str_val = wxString::Format(wxT("%.1f"), *double_val);
         return wxGenericValidator::TransferToWindow();
     }
+    return true;
 }
 
 bool wxPositiveDoubleValidator::TransferFromWindow()