pcsx2: Fix a few crashes in macOS. (PCSX2#3424)

* Fix crash on shutdown in macOS

* Fix crashing in ISO list on macOS

* Use MAP_FIXED on linux too
It works as expected and has no race conditions.

common/src/Utilities/Linux/LnxHostSys.cpp

@@ -178,21 +178,12 @@ bool HostSys::MmapCommitPtr(void *base, size_t size, const PageProtectionMode &m
 
 void HostSys::MmapResetPtr(void *base, size_t size)
 {
-    // On linux the only way to reset the memory is to unmap and remap it as PROT_NONE.
-    // That forces linux to unload all committed pages and start from scratch.
-
-    // FIXME: Ideally this code would have some threading lock on it to prevent any other
-    // malloc/free code in the current process from interfering with the operation, but I
-    // can't think of any good way to do that.  (generally it shouldn't be a problem in
-    // PCSX2 anyway, since MmapReset is only called when the ps2vm is suspended; so that
-    // pretty well stops all PCSX2 threads anyway).
+    PageSizeAssertionTest(size);
 
-    Munmap(base, size);
-    void *result = MmapReservePtr(base, size);
+    void *result = mmap(base, size, PROT_NONE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0);
 
     pxAssertRel((uptr)result == (uptr)base, pxsFmt(
-                                                "Virtual memory decommit failed: memory at 0x%08X -> 0x%08X could not be remapped.  "
-                                                "This is likely caused by multi-thread memory contention.",
+                                                "Virtual memory decommit failed: memory at 0x%08X -> 0x%08X could not be remapped.",
                                                 base, (uptr)base + size));
 }
 

pcsx2/gui/RecentIsoList.cpp

@@ -89,7 +89,9 @@ void RecentIsoManager::RemoveAllFromMenu()
 	if( m_Menu == NULL ) return;
 
 	int cnt = m_Items.size();
-	for( int i=0; i<cnt; ++i )
+	// Note: Go backwards to work around https://trac.wxwidgets.org/ticket/18772
+	// Switch it back to forwards once that's fixed in a relased WX version
+	for( int i=cnt-1; i>=0; --i )
 	{
 		RecentItem& curitem( m_Items[i] );
 		if( curitem.ItemPtr == NULL ) continue;