adding preference option for dynamic input blocking

/inpblock is now having subcommands 'timeout' and 'dynamic'
with:

/inpblock timeout <milliseconds>

and

/inpblock dynamic <on|off>

Defaults are:

/inpblock timeout 500
/inpblock dynamic on

To get the old behavior specify:

/inpblock timeout 20
/inpblock dynamic off

The dynamic mode will block incrementally after something
should be written to the window or after a key was pressed. So pressing
a key would set the timeout to 0ms and after 10 timeouts to the next
bigger one.

Example (with dynamic mode on):

"/inpblock timeout 50"

timeout series:

10x 0ms
10x 10ms (0ms + 10 times since last keypress)
10x 30ms (10ms + 20 times since last keypress)
*x50ms until next key was pressed or

src/config/preferences.c

@@ -531,6 +531,7 @@ _get_group(preference_t pref)
         case PREF_ROSTER_BY:
         case PREF_RESOURCE_TITLE:
         case PREF_RESOURCE_MESSAGE:
+        case PREF_INPBLOCK_DYNAMIC:
             return PREF_GROUP_UI;
         case PREF_STATES:
         case PREF_OUTTYPE:
@@ -672,6 +673,8 @@ _get_key(preference_t pref)
             return "resource.title";
         case PREF_RESOURCE_MESSAGE:
             return "resource.message";
+        case PREF_INPBLOCK_DYNAMIC:
+            return "inpblock.dynamic";
         default:
             return NULL;
     }
@@ -696,6 +699,7 @@ _get_default_boolean(preference_t pref)
         case PREF_MUC_PRIVILEGES:
         case PREF_PRESENCE:
         case PREF_WRAP:
+        case PREF_INPBLOCK_DYNAMIC:
             return TRUE;
         default:
             return FALSE;

src/config/preferences.h

@@ -100,7 +100,8 @@ typedef enum {
     PREF_OTR_WARN,
     PREF_OTR_POLICY,
     PREF_RESOURCE_TITLE,
-    PREF_RESOURCE_MESSAGE
+    PREF_RESOURCE_MESSAGE,
+    PREF_INPBLOCK_DYNAMIC
 } preference_t;
 
 typedef struct prof_alias_t {