Fix a few compiler warnings in GCC 9

Apparently GCC 7 is EOL in Debian testing.

include/core/instance.hpp

@@ -2,6 +2,7 @@
 #define _instance__hpp__included__
 
 #include "library/threads.hpp"
+#include <cstring>
 
 class movie_logic;
 class memory_space;
@@ -55,7 +56,7 @@ public:
 	{
 		entry e;
 		e.ptr = ptr = reinterpret_cast<T*>(new char[sizeof(T) + 32]);
-		memset(ptr, 0, sizeof(T) + 32);
+		memset((char*)ptr, 0, sizeof(T) + 32);
 		e.free1 = null;
 		e.free2 = free2;
 		e.prev = list;

src/emulation/sky/music.cpp

@@ -504,7 +504,7 @@ namespace sky
 				downmix_l[i] = gain_factor * c.downmix_l[i];
 				downmix_r[i] = gain_factor * c.downmix_r[i];
 			}
-		} catch(opus::not_loaded l) {
+		} catch(opus::not_loaded& l) {
 			d = NULL;
 			channels = c.channels;
 		}
@@ -556,7 +556,7 @@ namespace sky
 		try {
 			if(d)
 				d->ctl(opus::reset);
-		} catch(opus::not_loaded e) {
+		} catch(opus::not_loaded& e) {
 		}
 	}
 
@@ -623,7 +623,7 @@ namespace sky
 	void music_player::decode(std::pair<int16_t, int16_t>* output, size_t samples)
 	{
 		if(!song) {
-			memset(output, 0, samples * sizeof(std::pair<int16_t, int16_t>));
+			memset((char*)output, 0, samples * sizeof(std::pair<int16_t, int16_t>));
 			return;
 		}
 		const subsong_transition* strans1 = &song->transitions(mem.subsong1);

src/lua/gui-core.cpp

@@ -127,8 +127,8 @@ namespace
 		P(a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7]);
 		for(unsigned i = 0; i < 8; i++) {
 			for(unsigned j = 0; j < 4; j++) {
-				b[j] |= ((a[i] >> 2*j+0) & 1) << 7-i;
-				b[j] |= ((a[i] >> 2*j+1) & 1) << 15-i;
+				b[j] |= ((a[i] >> (2*j+0)) & 1) << (7-i);
+				b[j] |= ((a[i] >> (2*j+1)) & 1) << (15-i);
 			}
 		}
 		for(unsigned i = 0; i < 4; i++) L.pushnumber(b[i]);

src/platform/wxwidgets/settings-downloads.cpp

@@ -30,7 +30,7 @@ namespace
 	};
 
 	wxeditor_esettings_download::wxeditor_esettings_download(wxWindow* parent, emulator_instance& _inst)
-		: settings_tab(parent, inst)
+		: settings_tab(parent, _inst)
 	{
 		CHECK_UI_THREAD;
 		wxSizer* top_s = new wxBoxSizer(wxVERTICAL);