patch 9.0.2124: INT overflow detection logic can be simplified

Problem:  INT overflow logic can be simplified
Solution: introduce trim_to_int() function

closes: #13556

Signed-off-by: Ernie Rael <errael@raelity.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/misc1.c

@@ -2838,3 +2838,11 @@ vim_append_digit_long(long *value, int digit)
     *value = x * 10 + (long)digit;
     return OK;
 }
+
+// Return something that fits into an int.
+    int
+trim_to_int(long long x)
+{
+    return x > INT_MAX ? INT_MAX : x < INT_MIN ? INT_MIN : x;
+}
+