changes default PC's Menu bindings to reflect Modern games' Menu UI design

Those who are playing the PC Port of Perfect Dark for the first time, but coming from newer PC Versions' menu bindings will find out Menu bindings don't confined towards a modern standard. This PR addresses it while retaining backwards compatibility.

the RETURN/ENTER key will become a proper CONFIRM action, as opposed to emulating as a START button. (the emulated START button will still be TAB key), while Right Mouse Click now behaves as a CANCEL key. 

This won't affect existing Perfect Dark PC Players' existing bindings. but the next time you reset the default Key Bindings will experience a more streamlined setup.

port/src/input.c

@@ -195,7 +195,7 @@ void inputSetDefaultKeyBinds(s32 cidx, s32 n64mode)
 		{ CK_RTRIG,         VK_MOUSE_RIGHT,      SDL_SCANCODE_Z      },
 		{ CK_LTRIG,         SDL_SCANCODE_F,      SDL_SCANCODE_X      },
 		{ CK_ZTRIG,         VK_MOUSE_LEFT,       SDL_SCANCODE_SPACE  },
-		{ CK_START,         SDL_SCANCODE_RETURN, SDL_SCANCODE_TAB    },
+		{ CK_START,         SDL_SCANCODE_TAB,    0                   },
 		{ CK_DPAD_D,        SDL_SCANCODE_Q,      VK_MOUSE_MIDDLE     },
 		{ CK_DPAD_U,        0,                   0                   },
 		{ CK_Y,             VK_MOUSE_WHEEL_DN,   0                   },
@@ -209,7 +209,9 @@ void inputSetDefaultKeyBinds(s32 cidx, s32 n64mode)
 		{ CK_STICK_YNEG,    SDL_SCANCODE_DOWN,   0                   },
 		{ CK_STICK_YPOS,    SDL_SCANCODE_UP,     0                   },
 		{ CK_4000,          SDL_SCANCODE_LSHIFT, 0                   },
-		{ CK_2000,          SDL_SCANCODE_LCTRL,  0                   }
+		{ CK_2000,          SDL_SCANCODE_LCTRL,  0                   },
+		{ CK_ACCEPT,        SDL_SCANCODE_RETURN, SDL_SCANCODE_E      },
+		{ CK_CANCEL,        VK_MOUSE_RIGHT,      0                   },
 	};
 
 	static const u32 pcjoybinds[][2] = {