misc: eliminate all those remaining gcc -Wall warnings

Reference(s):
proc/readproc.c: In function 'statm2proc'
proc/readproc.c:600:9: warning: variable 'num' set but not used [-Wunused-but-set-variable]

proc/stat.c: In function 'stat_derive_unique':
proc/stat.c:429:1: warning: no return statement in function returning non-void [-Wreturn-type]

ps/parser.c: In function 'arg_type':
ps/parser.c:1098:3: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
ps/parser.c:1099:34: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'

lib/signals.c: In function 'strtosig':
lib/signals.c:243:9: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
lib/signals.c:245:13: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'

slabtop.c: In function 'print_summary':
slabtop.c:223:29: warning: unused variable 'stats' [-Wunused-variable]

watch.c: In function 'process_ansi':
watch.c:232:5: warning: this 'if' clause does not guard... [-Wmisleading-indentation]
watch.c:235:2: note: ...this statement, but the latter is misleadingly indented as if it is guarded by the 'if'

Signed-off-by: Jim Warner <james.warner@comcast.net>

lib/signals.c

@@ -242,7 +242,7 @@ char *strtosig(const char *restrict s)
         numsignal = strtol(s,&endp,10);
         if(*endp || endp==s)
             free(p);
-            return NULL; /* not valid */
+        return NULL; /* not valid */
     }
     if (numsignal){
         for (i = 0; i < number_of_signals; i++){