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>
diff --git a/src/proto/misc1.pro b/src/proto/misc1.pro
index 2b8e9d8..c602b0e 100644
--- a/src/proto/misc1.pro
+++ b/src/proto/misc1.pro
@@ -55,4 +55,5 @@
 void may_trigger_modechanged(void);
 int vim_append_digit_int(int *value, int digit);
 int vim_append_digit_long(long *value, int digit);
+int trim_to_int(long long x);
 /* vim: set ft=c : */