Avoid implicit function declarations in lang.c.  Future compilers will

not support them by default, leading to build failures.

Submitted upstream: <https://gitlab.com/alevt/alevt/-/merge_requests/10>

diff --git a/lang.c b/lang.c

index 847fd52a7d2d1142..9882dc85a7b08929 100644

--- a/lang.c

+++ b/lang.c

@@ -4,6 +4,9 @@

 #include "vt.h"

 #include "lang.h"

+static int is_greek(int c);

+static int is_koi(int c);

+

 int latin1 = -1;

 static u8 lang_char[256];

@@ -197,14 +200,14 @@ else if ((latin1 == GREEK) && lang==15) { /* Hellas */

 }

 /* check for Greek chars - needs locale iso8859-7 set */

-int is_greek(int c)

+static int is_greek(int c)

 {

   if( isalpha(c | 0x80)) return 1;

   return 0;

 }

 /* check for russian chars - needs locale KOI8-R set */

-int is_koi(int c)

+static int is_koi(int c)

 {

   if( isalpha(c | 0x80)) return 1;

   if( c=='&' ) return 1;