patch 8.1.1836: inaccurate memory estimate for Amiga-like OS

Problem:    Inaccurate memory estimate for Amiga-like OS.
Solution:   Adjust #ifdef for AvailMem(). (Ola Söder, closes #4797)
diff --git a/src/version.c b/src/version.c
index f10ea08..852595d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -770,6 +770,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1836,
+/**/
     1835,
 /**/
     1834,