Fix tab key

When Shift + Tab is pressed X server send the event XK_ISO_Left_Tab with
ShiftMask, so this is the entry we need in config.def.h

This patch also revert the previous patch for this issue because it breaks
the keyboard.
---
 config.def.h |    2 +-
 st.c         |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

1 files changed, 1 insertions, 1 deletions

diff --git a/config.def.h b/config.def.h
index 5d887fc..972285b 100644
--- a/config.def.h
+++ b/config.def.h
@@ -141,7 +141,7 @@ static Key key[] = {
         { XK_Right,         ShiftMask,      "\033[1;2C",     0,    0,    0},
         { XK_Right,         ControlMask,    "\033[1;5C",     0,    0,    0},
         { XK_Right,         Mod1Mask,       "\033[1;3C",     0,    0,    0},
-        { XK_Tab,           ShiftMask,      "\033[Z",        0,    0,    0},
+        { XK_ISO_Left_Tab,  ShiftMask,      "\033[Z",        0,    0,    0},
         { XK_Return,        XK_NO_MOD,      "\n",            0,    0,   -1},
         { XK_Return,        XK_NO_MOD,      "\r\n",          0,    0,   +1},
         { XK_Return,        Mod1Mask,       "\033\n",        0,    0,   -1},