fix(core): remove shutdown()

In a very weird situation, our declaration of `shutdown()` shadows a
function `shutdown(int, int)` from sys/socket, which _just happens_ to
be called by libxcb when closing the sdl window. This calls
`main_clean_exit` which calls into micropython and causes at best an
uncaught NLR and at worst an outright segfault because by that time the
micropython environment doesn't exist anymore.

I didn't think this sort of thing would be possible but here we are??

Fixed by removing `__shutdown()` and replacing `shutdown` with
`trezor_shutdown`

core/embed/rust/src/trezorhal/fatal_error.rs

@@ -1,7 +1,7 @@
 mod ffi {
     extern "C" {
         // trezorhal/common.c
-        pub fn shutdown() -> !;
+        pub fn trezor_shutdown() -> !;
     }
 }
 
@@ -13,7 +13,7 @@ use heapless::String;
 use crate::ui::util::u32_to_str;
 
 fn shutdown() -> ! {
-    unsafe { ffi::shutdown() }
+    unsafe { ffi::trezor_shutdown() }
 }
 
 #[cfg(feature = "bootloader")]

core/embed/trezorhal/common.c

@@ -43,7 +43,7 @@
 // from util.s
 extern void shutdown_privileged(void);
 
-void __attribute__((noreturn)) shutdown(void) {
+void __attribute__((noreturn)) trezor_shutdown(void) {
 #ifdef USE_SVC_SHUTDOWN
   svc_shutdown();
 #else
@@ -88,7 +88,7 @@ __fatal_error(const char *expr, const char *msg, const char *file, int line,
 #endif
   display_printf("\nPlease contact Trezor support.\n");
 #endif
-  shutdown();
+  trezor_shutdown();
 }
 
 void __attribute__((noreturn))
@@ -108,7 +108,7 @@ error_shutdown(const char *label, const char *msg) {
   display_printf("\nPlease unplug the device.\n");
 #endif
   display_backlight(255);
-  shutdown();
+  trezor_shutdown();
 }
 
 #ifndef NDEBUG

core/embed/trezorhal/common.h

@@ -51,7 +51,7 @@
 
 #define STAY_IN_BOOTLOADER_FLAG 0x0FC35A96
 
-void __attribute__((noreturn)) shutdown(void);
+void __attribute__((noreturn)) trezor_shutdown(void);
 
 void __attribute__((noreturn))
 __fatal_error(const char *expr, const char *msg, const char *file, int line,

core/embed/unix/common.c

@@ -34,15 +34,13 @@
 extern void main_clean_exit();
 extern float DISPLAY_GAMMA;
 
-void __attribute__((noreturn)) __shutdown(void) {
+void __attribute__((noreturn)) trezor_shutdown(void) {
   printf("SHUTDOWN\n");
   main_clean_exit(3);
   for (;;)
     ;
 }
 
-void __attribute__((noreturn)) shutdown(void) { __shutdown(); }
-
 #ifdef RGB16
 #define COLOR_FATAL_ERROR RGB16(0x7F, 0x00, 0x00)
 #else
@@ -92,7 +90,7 @@ __fatal_error(const char *expr, const char *msg, const char *file, int line,
   printf("Hint:\nIsn't the emulator already running?\n");
 #endif
   hal_delay(3000);
-  shutdown();
+  trezor_shutdown();
 }
 
 void __attribute__((noreturn))
@@ -135,15 +133,15 @@ uint32_t hal_ticks_ms() {
 static int SDLCALL emulator_event_filter(void *userdata, SDL_Event *event) {
   switch (event->type) {
     case SDL_QUIT:
-      __shutdown();
+      trezor_shutdown();
       return 0;
     case SDL_KEYUP:
       if (event->key.repeat) {
         return 0;
       }
       switch (event->key.keysym.sym) {
         case SDLK_ESCAPE:
-          __shutdown();
+          trezor_shutdown();
           return 0;
         case SDLK_p:
           display_save("emu");

core/embed/unix/common.h

@@ -40,7 +40,7 @@
   })
 #endif
 
-void __attribute__((noreturn)) shutdown(void);
+void __attribute__((noreturn)) trezor_shutdown(void);
 
 void __attribute__((noreturn))
 __fatal_error(const char *expr, const char *msg, const char *file, int line,

core/embed/unix/touch/touch.c

@@ -21,9 +21,6 @@
 #include <stdbool.h>
 #include <stdint.h>
 
-extern void __shutdown(void);
-extern const char *display_save(const char *prefix);
-
 #if defined TREZOR_MODEL_T
 
 #include "touch.h"