patch 8.2.2388: no easy way to get the maximum or mininum number value

Problem:    No easy way to get the maximum or mininum number value.
Solution:   Add v:numbermax and v:numbermin.
diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 217e69d..dd5bc93 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -1,4 +1,4 @@
-*eval.txt*	For Vim version 8.2.  Last change: 2021 Jan 17
+*eval.txt*	For Vim version 8.2.  Last change: 2021 Jan 21
 
 
 		  VIM REFERENCE MANUAL	  by Bram Moolenaar
@@ -2082,6 +2082,12 @@
 		That is so that eval() can parse the string back to the same
 		value.  Read-only.
 
+					*v:numbermax* *numbermax-variable*
+v:numbermax	Maximum value of a number.
+
+					*v:numbermix* *numbermix-variable*
+v:numbermin	Minimum value of a number (negative)
+
 					*v:numbersize* *numbersize-variable*
 v:numbersize	Number of bits in a Number.  This is normally 64, but on some
 		systems it may be 32.