Resolve a problem in F2/Setup update interval adjustments

The halfdelay(3X) curses function ultimately drives the update
interval that htop samples values and refreshes at.  This is a
bit complicated by interrupts generated from other places (key
or mouse events), however if halfdelay is not explicitly called
at some point soon after changing the interval it does not get
correctly updated during that session.

Since the delay setting is persisted, on restart htop actually
does honour the change from the previous invocation, confusing
the situation even further.

With this commit the update is reflected immediately in the UI
as well now.

Fixes: #1510

CRT.h

@@ -214,6 +214,10 @@ void CRT_disableDelay(void);
 
 void CRT_enableDelay(void);
 
+static inline void CRT_updateDelay(void) {
+   CRT_enableDelay(); // pushes new delay setting into halfdelay(3X)
+}
+
 void CRT_setColors(int colorScheme);
 
 #endif

DisplayOptionsPanel.c

@@ -74,6 +74,7 @@ static HandlerResult DisplayOptionsPanel_eventHandler(Panel* super, int ch) {
    if (result == HANDLED) {
       this->settings->changed = true;
       this->settings->lastUpdate++;
+      CRT_updateDelay();
       Header* header = this->scr->header;
       Header_calculateHeight(header);
       Header_reinit(header);