patch 8.2.0814: clang warning for implicit conversion

Problem:    Clang warning for implicit conversion.
Solution:   Add type cast. (Dominique Pelle, closes #6124)
diff --git a/src/evalfunc.c b/src/evalfunc.c
index 37cb72f..11452ce 100644
--- a/src/evalfunc.c
+++ b/src/evalfunc.c
@@ -2603,9 +2603,9 @@
 
     if (get_float_arg(argvars, &f) == OK)
     {
-	if (f <= -VARNUM_MAX + DBL_EPSILON)
+	if (f <= (float_T)-VARNUM_MAX + DBL_EPSILON)
 	    rettv->vval.v_number = -VARNUM_MAX;
-	else if (f >= VARNUM_MAX - DBL_EPSILON)
+	else if (f >= (float_T)VARNUM_MAX - DBL_EPSILON)
 	    rettv->vval.v_number = VARNUM_MAX;
 	else
 	    rettv->vval.v_number = (varnumber_T)f;