Fix ancient declaration inconsistency in cube & seg ... came across a

compiler that warns about it.

contrib/cube/cubeparse.y

@@ -13,8 +13,7 @@
 #undef yylex                 /* falure to redefine yylex will result in a call to  the */
 #define yylex cube_yylex     /* wrong scanner when running inside the postgres backend  */
 
-extern int yylex();           /* defined as cube_yylex in cubescan.c */
-extern int errno;
+extern int yylex(void);      /* defined as cube_yylex in cubescan.l */
 
 static char *scanbuf;
 static int	scanbuflen;

contrib/seg/segparse.y

@@ -10,8 +10,7 @@
 #undef yylex                  /* falure to redefine yylex will result in calling the */
 #define yylex seg_yylex       /* wrong scanner when running inside postgres backend  */
 
-  extern int errno;
-  extern int yylex();           /* defined as seg_yylex in segscan.c */
+  extern int yylex(void);     /* defined as seg_yylex in segscan.l */
   extern int significant_digits( char *str );    /* defined in seg.c */
   
   void seg_yyerror(const char *message);