Ports: Remove SRB2 mouse hacks

This patch builds off the previous commit and removes the mouse hacks
entirely as they are not needed anymore.

With this, Sonic Robo Blast 2 now correctly locks the mouse inside the
game and makes for a much better playing experience! :^)

Ports/SRB2/patches/0004-i_system.c-hacks.patch

@@ -0,0 +1,88 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Refrag <R3FR4GYT@gmail.com>
+Date: Sun, 4 Feb 2024 17:45:18 +0100
+Subject: [PATCH] i_system.c hacks
+
+This patch disables / removes some code to get the game to build without issues.
+These don't seem to matter much anyway as the game still runs.
+---
+ src/sdl/i_system.c | 19 +++++++------------
+ 1 file changed, 7 insertions(+), 12 deletions(-)
+
+diff --git a/src/sdl/i_system.c b/src/sdl/i_system.c
+index 902194f4f..e2306aa9c 100644
+--- a/src/sdl/i_system.c
++++ b/src/sdl/i_system.c
+@@ -83,14 +83,11 @@ typedef LPVOID (WINAPI *p_MapViewOfFile) (HANDLE, DWORD, DWORD, DWORD, SIZE_T);
+ #include <sys/vfs.h>
+ #else
+ #include <sys/param.h>
+-#include <sys/mount.h>
+ /*For meminfo*/
+ #include <sys/types.h>
+ #ifdef FREEBSD
+ #include <kvm.h>
+ #endif
+-#include <nlist.h>
+-#include <sys/sysctl.h>
+ #endif
+ #endif
+ 
+@@ -138,7 +135,6 @@ typedef LPVOID (WINAPI *p_MapViewOfFile) (HANDLE, DWORD, DWORD, DWORD, SIZE_T);
+ #endif
+ 
+ #if defined (__unix__) || defined(__APPLE__) || defined (UNIXCOMMON)
+-#include <execinfo.h>
+ #include <time.h>
+ #define UNIXBACKTRACE
+ #endif
+@@ -267,6 +263,7 @@ UINT8 keyboard_started = false;
+ 
+ static void write_backtrace(INT32 signal)
+ {
++#if 0
+ 	int fd = -1;
+ 	size_t size;
+ 	time_t rawtime;
+@@ -316,6 +313,7 @@ static void write_backtrace(INT32 signal)
+ 	CRASHLOG_WRITE("\n"); // Write another newline to the log so it looks nice :)
+ 
+ 	close(fd);
++#endif
+ }
+ #undef STDERR_WRITE
+ #undef CRASHLOG_WRITE
+@@ -2066,6 +2064,8 @@ void I_StartupMouse2(void)
+ 			else
+ 				rts = 1;
+ 		}
++	
++		#if 0
+ 		if (dtr != -1 || rts != -1)
+ 		{
+ 			INT32 c;
+@@ -2082,6 +2082,7 @@ void I_StartupMouse2(void)
+ 				c |= TIOCM_RTS;
+ 			ioctl(fdmouse2, TIOCMSET, &c);
+ 		}
++		#endif
+ 	}
+ 	mouse2_started = 1;
+ 	I_AddExitFunc(I_ShutdownMouse2);
+@@ -2671,14 +2672,8 @@ void I_GetDiskFreeSpace(INT64 *freespace)
+ #if defined (SOLARIS) || defined (__HAIKU__)
+ 	*freespace = INT32_MAX;
+ 	return;
+-#else // Both Linux and BSD have this, apparently.
+-	struct statfs stfs;
+-	if (statfs(srb2home, &stfs) == -1)
+-	{
+-		*freespace = INT32_MAX;
+-		return;
+-	}
+-	*freespace = stfs.f_bavail * stfs.f_bsize;
++#else
++	*freespace = 1024*1024*1024;
+ #endif
+ #elif defined (_WIN32)
+ 	static p_GetDiskFreeSpaceExA pfnGetDiskFreeSpaceEx = NULL;