patch 8.1.1903: cannot build without the +eval feature

Problem:    Cannot build without the +eval feature.
Solution:   Add missing #ifdefs
diff --git a/src/version.c b/src/version.c
index 0b15d71..56f6972 100644
--- a/src/version.c
+++ b/src/version.c
@@ -762,6 +762,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    1903,
+/**/
     1902,
 /**/
     1901,