patch 8.0.1350: cannot build with +eval and -multi_byte

Problem:    Cannot build with +eval and -multi_byte.
Solution:   Adjust #ifdefs. (John Marriott)  Always include the multi_byte
            feature when an input method feature is enabled.
diff --git a/src/mbyte.c b/src/mbyte.c
index 408c49a..742c220 100644
--- a/src/mbyte.c
+++ b/src/mbyte.c
@@ -4790,7 +4790,7 @@
 # define USE_IMSTATUSFUNC (*p_imsf != NUL)
 #endif
 
-#ifdef FEAT_EVAL
+#if defined(FEAT_EVAL) && defined(FEAT_MBYTE)
     static void
 call_imactivatefunc(int active)
 {
@@ -6486,7 +6486,7 @@
     int
 im_get_status()
 {
-#  ifdef FEAT_EVAL
+#  if defined(FEAT_MBYTE) && defined(FEAT_EVAL)
     if (USE_IMSTATUSFUNC)
 	return call_imstatusfunc();
 #  endif