- cleanup of sound system startup and menu handling:

* added global functions that check whether FMod and OpenAL are present, without initializing the sound backend.
* make sound init code more fault tolerant. It will now try to switch between FMod and OpenAL if the currently active one cannot be found but the other one can.
* added 'ifoption' checks for sound backend to menu code.
* only show sound backends which are present and hide the options for the ones which are not.

src/menu/menudef.cpp

@@ -49,6 +49,7 @@
 #include "i_music.h"
 #include "m_joy.h"
 #include "gi.h"
+#include "i_sound.h"
 
 #include "optionmenuitems.h"
 
@@ -170,6 +171,14 @@ static bool CheckSkipOptionBlock(FScanner &sc)
 				filter = true;
 			#endif
 		}
+		else if (sc.Compare("OpenAL"))
+		{
+			filter |= IsOpenALPresent();
+		}
+		else if (sc.Compare("FModEx"))
+		{
+			filter |= IsFModExPresent();
+		}
 	}
 	while (sc.CheckString(","));
 	sc.MustGetStringName(")");
@@ -591,7 +600,11 @@ static void ParseOptionSettings(FScanner &sc)
 	while (!sc.CheckString("}"))
 	{
 		sc.MustGetString();
-		if (sc.Compare("ifgame"))
+		if (sc.Compare("else"))
+		{
+			SkipSubBlock(sc);
+		}
+		else if (sc.Compare("ifgame"))
 		{
 			if (!CheckSkipGameBlock(sc))
 			{
@@ -628,7 +641,11 @@ static void ParseOptionMenuBody(FScanner &sc, FOptionMenuDescriptor *desc)
 	while (!sc.CheckString("}"))
 	{
 		sc.MustGetString();
-		if (sc.Compare("ifgame"))
+		if (sc.Compare("else"))
+		{
+			SkipSubBlock(sc);
+		}
+		else if (sc.Compare("ifgame"))
 		{
 			if (!CheckSkipGameBlock(sc))
 			{