Make SNES rom memory domain writeable

Use at your own risk

src/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesApi.cs

@@ -68,8 +68,8 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 				SbrkHeapSizeKB = 4 * 1024,
 				InvisibleHeapSizeKB = 8 * 1024,
 				MmapHeapSizeKB = 32 * 1024, // TODO: see if we can safely make libco stacks smaller
-				PlainHeapSizeKB = 2 * 1024, // TODO: wasn't there more in here?
-				SealedHeapSizeKB = 128 * 1024,
+				PlainHeapSizeKB = 32 * 1024, // TODO: This can be smaller, probably; needs to be as big as largest ROM + 2MB, or less
+				SealedHeapSizeKB = 80 * 1024,
 				SkipCoreConsistencyCheck = comm.CorePreferences.HasFlag(CoreComm.CorePreferencesFlags.WaterboxCoreConsistencyCheck),
 				SkipMemoryConsistencyCheck = comm.CorePreferences.HasFlag(CoreComm.CorePreferencesFlags.WaterboxMemoryConsistencyCheck),
 			});

src/BizHawk.Emulation.Cores/Consoles/Nintendo/SNES/LibsnesCore.IMemoryDomains.cs

@@ -92,7 +92,7 @@ namespace BizHawk.Emulation.Cores.Nintendo.SNES
 			byte* blockPtr = Api.QUERY_get_memory_data(id);
 
 			var md = new MemoryDomainIntPtrMonitor(name, MemoryDomain.Endian.Little, (IntPtr)blockPtr, size,
-				id != LibsnesApi.SNES_MEMORY.CARTRIDGE_ROM, // hack: for just this one memory area, it will be readonly
+				true,
 				byteSize, Api);
 
 			_memoryDomainList.Add(md);

waterbox/libsnes/bsnes/target-libsnes/libsnes_pwrap.cpp

@@ -297,10 +297,7 @@ void* snes_allocSharedMemory(const char* memtype, size_t amt)
 
 	void* ret;
 
-	if (strcmp(memtype, "CARTRIDGE_ROM") == 0)
-		ret = alloc_sealed(amt);
-	else
-		ret = alloc_plain(amt);
+	ret = alloc_plain(amt);
 
 	comm.str = (char*)memtype;
 	comm.size = amt;