patch 8.0.1312: balloon_show() only works in terminal when compiled with GUI

Problem:    balloon_show() only works in terminal when compiled with the GUI.
Solution:   Add FEAT_BEVAL_GUI and refactor to move common code out of the GUI
            specific file.
diff --git a/src/option.c b/src/option.c
index 495a89d..e09191f 100644
--- a/src/option.c
+++ b/src/option.c
@@ -634,7 +634,7 @@
 #endif
 			    SCRIPTID_INIT},
     {"ballooneval", "beval",P_BOOL|P_VI_DEF|P_NO_MKRC,
-#ifdef FEAT_BEVAL
+#ifdef FEAT_BEVAL_GUI
 			    (char_u *)&p_beval, PV_NONE,
 			    {(char_u *)FALSE, (char_u *)0L}
 #else
@@ -643,7 +643,7 @@
 #endif
 			    SCRIPTID_INIT},
     {"balloonevalterm", "bevalterm",P_BOOL|P_VI_DEF|P_NO_MKRC,
-#ifdef FEAT_BEVALTERM
+#ifdef FEAT_BEVAL_TERM
 			    (char_u *)&p_bevalterm, PV_NONE,
 			    {(char_u *)FALSE, (char_u *)0L}
 #else
@@ -8429,7 +8429,7 @@
 	p_wiv = (*T_XS != NUL);
     }
 
-#ifdef FEAT_BEVAL
+#ifdef FEAT_BEVAL_GUI
     else if ((int *)varp == &p_beval)
     {
 	if (!balloonEvalForTerm)
@@ -8441,12 +8441,12 @@
 	}
     }
 #endif
-# ifdef FEAT_BEVALTERM
+#ifdef FEAT_BEVAL_TERM
     else if ((int *)varp == &p_bevalterm)
     {
 	mch_bevalterm_changed();
     }
-# endif
+#endif
 
 #ifdef FEAT_AUTOCHDIR
     else if ((int *)varp == &p_acd)