sowm: Enable missing prototypes warning and define win_prev.

Makefile

@@ -1,4 +1,4 @@
-CFLAGS+= -std=c99 -Wall -Wextra -pedantic
+CFLAGS+= -std=c99 -Wall -Wextra -Wmissing-prototypes -pedantic
 LDADD+= -lX11
 LDFLAGS=
 PREFIX?= /usr

config.def.h

@@ -17,7 +17,9 @@ static struct key keys[] = {
     {MOD,      XK_q,   win_kill,   {0}},
     {MOD,      XK_c,   win_center, {0}},
     {MOD,      XK_f,   win_fs,     {0}},
-    {Mod1Mask, XK_Tab, win_next,   {0}},
+
+    {Mod1Mask,           XK_Tab, win_next,   {0}},
+    {Mod1Mask|ShiftMask, XK_Tab, win_prev,   {0}},
 
     {MOD, XK_d,      run, {.com = menu}},
     {MOD, XK_w,      run, {.com = colors}},

sowm.c

@@ -212,7 +212,7 @@ void win_to_ws(const Arg arg) {
 
 void win_prev() {
     if (!cur) return;
-    
+
     XRaiseWindow(d, cur->prev->w);
     win_focus(cur->prev);
 }