Fix (potential) problematic use cases of qboolean.

Until 853f832 qboolean was always defined as an enum. Starting with
853f832 it may be defined as bool when building in C23 mode or any
newer standard. There are subtle behavioral differences between enum
and bool, fix these:

* The enum has int as underlying type, floats are cut down to the
  nearest int. Thus 0.5f becomes false. With bool everything which
  is not 0 becomes true. Gone through the code and made sure that
  there are no float to qboolean type conversions.
* Always use true and false, not something else like 1 and 0 or
  (when building under Windows) TRUE and FALSE.
* Fix some corner cases where integers >1 where missused as true.
  These should be noops.
* Fix `R_GreyscaledLight()` misusing qboolean for returning int.

Partly based upon yquake2/yquake2remaster@e3c8d26

Closes #1191

src/backends/unix/network.c

@@ -397,7 +397,7 @@ NET_StringToSockaddr(const char *s, struct sockaddr_storage *sadr)
 		if (!*space)
 		{
 			Com_Printf("NET_StringToSockaddr: invalid IPv6 address %s\n", s);
-			return 0;
+			return false;
 		}
 
 		*space++ = '\0';
@@ -417,7 +417,7 @@ NET_StringToSockaddr(const char *s, struct sockaddr_storage *sadr)
 		/* Error */
 		Com_Printf("NET_StringToSockaddr: string %s:\n%s\n", s,
 				gai_strerror(err));
-		return 0;
+		return false;
 	}
 
 	switch (resultp->ai_family)
@@ -432,7 +432,7 @@ NET_StringToSockaddr(const char *s, struct sockaddr_storage *sadr)
 		default:
 			Com_Printf("NET_StringToSockaddr: string %s:\nprotocol family %d not supported\n",
 				s, resultp->ai_family);
-			return 0;
+			return false;
 	}
 
 	freeaddrinfo(resultp);

src/backends/unix/shared/hunk.c

@@ -79,7 +79,7 @@ Hunk_Begin(int maxsize)
 	prot |= PROT_MAX(prot);
 #endif
 
-	membase = mmap(0, maxhunksize, prot,
+	membase = (byte *)mmap(0, maxhunksize, prot,
 			flags, -1, 0);
 
 	if ((membase == NULL) || (membase == (byte *)-1))

src/backends/windows/network.c

@@ -193,7 +193,7 @@ NET_CompareAdr(netadr_t a, netadr_t b)
 
 	if (a.type == NA_LOOPBACK)
 	{
-		return TRUE;
+		return true;
 	}
 
 	if (a.type == NA_IP)
@@ -240,7 +240,7 @@ NET_CompareBaseAdr(netadr_t a, netadr_t b)
 
 	if (a.type == NA_LOOPBACK)
 	{
-		return TRUE;
+		return true;
 	}
 
 	if (a.type == NA_IP)
@@ -411,7 +411,7 @@ NET_StringToSockaddr(const char *s, struct sockaddr_storage *sadr)
 		if (!*space)
 		{
 			Com_Printf("NET_StringToSockaddr: invalid IPv6 address %s\n", s);
-			return 0;
+			return false;
 		}
 
 		*space++ = '\0';
@@ -431,7 +431,7 @@ NET_StringToSockaddr(const char *s, struct sockaddr_storage *sadr)
 		/* Error */
 		Com_Printf("NET_StringToSockaddr: string %s:\n%s\n", s,
 				gai_strerror(err));
-		return 0;
+		return false;
 	}
 
 	switch (resultp->ai_family)

src/client/curl/download.c

@@ -1179,7 +1179,7 @@ qboolean CL_PendingHTTPDownloads(void)
 		return false;
 	}
 
-	return pendingCount + handleCount;
+	return ((pendingCount + handleCount) > 0);
 }
 
 /*

src/client/refresh/soft/sw_surf.c

@@ -39,7 +39,7 @@ surfcache_t	*sc_base;
 /*
  * Color light apply is not required
  */
-static qboolean
+static int
 R_GreyscaledLight(const light3_t light)
 {
 	light3_t light_masked;

src/client/sound/sdl.c

@@ -1344,7 +1344,7 @@ SDL_BackendInit(void)
 	   but this is Quake 2 ... */
 	if (snd_inited)
 	{
-		return 1;
+		return true;
 	}
 
 	int sndbits = (Cvar_Get("sndbits", "16", CVAR_ARCHIVE))->value;
@@ -1369,7 +1369,7 @@ SDL_BackendInit(void)
 #endif
 		{
 			Com_Printf ("Couldn't init SDL audio: %s.\n", SDL_GetError ());
-			return 0;
+			return false;
 		}
 	}
 	const char* drivername = SDL_GetCurrentAudioDriver();
@@ -1432,7 +1432,7 @@ SDL_BackendInit(void)
 	{
 		Com_Printf("SDL_OpenAudio() failed: %s\n", SDL_GetError());
 		SDL_QuitSubSystem(SDL_INIT_AUDIO);
-		return 0;
+		return false;
 	}
 
 	/* This points to the frontend */
@@ -1473,7 +1473,7 @@ SDL_BackendInit(void)
 	soundtime = 0;
 	snd_inited = 1;
 
-	return 1;
+	return true;
 }
 
 /*
@@ -1508,7 +1508,7 @@ SDL_BackendInit(void)
 	   but this is Quake 2 ... */
 	if (snd_inited)
 	{
-		return 1;
+		return true;
 	}
 
 	int sndbits = (Cvar_Get("sndbits", "16", CVAR_ARCHIVE))->value;
@@ -1529,7 +1529,7 @@ SDL_BackendInit(void)
 		if (SDL_Init(SDL_INIT_AUDIO) == -1)
 		{
 			Com_Printf ("Couldn't init SDL audio: %s.\n", SDL_GetError ());
-			return 0;
+			return false;
 		}
 	}
 	const char* drivername = SDL_GetCurrentAudioDriver();
@@ -1592,7 +1592,7 @@ SDL_BackendInit(void)
 	{
 		Com_Printf("SDL_OpenAudio() failed: %s\n", SDL_GetError());
 		SDL_QuitSubSystem(SDL_INIT_AUDIO);
-		return 0;
+		return false;
 	}
 
 	/* This points to the frontend */
@@ -1633,7 +1633,7 @@ SDL_BackendInit(void)
 	soundtime = 0;
 	snd_inited = 1;
 
-	return 1;
+	return true;
 }
 
 /*

src/common/cmdparser.c

@@ -54,7 +54,6 @@ int alias_count; /* for detecting runaway loops */
 cmdalias_t *cmd_alias;
 int cmd_wait;
 static int cmd_argc;
-static int cmd_argc;
 static char *cmd_argv[MAX_STRING_TOKENS];
 static char *cmd_null_string = "";
 static char cmd_args[MAX_STRING_CHARS];

src/game/g_svcmds.c

@@ -176,11 +176,11 @@ SV_FilterPacket(char *from)
 	{
 		if ((in & ipfilters[i].mask) == ipfilters[i].compare)
 		{
-			return (int)filterban->value;
+			return (filterban->value != 0);
 		}
 	}
 
-	return (int)!filterban->value;
+	return (filterban->value == 0);
 }
 
 void