revert fix for #H4041 - decl for has_color()

Since the attempted fix for the warning about has_color() being
implicitly declared introduced a worse problem of conflicting
declaration in cases where it's already declared, back that change
out.

doc/fixes36.1

@@ -138,7 +138,6 @@ tty: responding with <return> or <enter> during role, race, &c selection
 	behaved same as <escape> to quit; now it will pick [random] instead
 unix/X11: in top level Makefile, some commented out definitions of VARDATND
 	misspelled pilemark.xbm (as pilemark.xpm)
-unix/tty: fix compile warning about 'has_colors' for some configurations
 unix: options file with CR+LF line ends and an invalid option line resulted in
 	"ad option line: "whatever-the-line-was
 	because embedded carriage return character changed cursor's position

sys/share/unixtty.c

@@ -335,9 +335,6 @@ int sco_flag_console = 0;
 int sco_map_valid = -1;
 unsigned char sco_chanmap_buf[BSIZE];
 
-#if defined(TTY_GRAPHICS) && defined(TEXTCOLOR)
-extern int NDECL(has_colors);
-#endif
 void NDECL(sco_mapon);
 void NDECL(sco_mapoff);
 void NDECL(check_sco_console);
@@ -402,9 +399,6 @@ init_sco_cons()
 
 int linux_flag_console = 0;
 
-#if defined(TTY_GRAPHICS) && defined(TEXTCOLOR)
-extern int NDECL(has_colors);
-#endif
 void NDECL(linux_mapon);
 void NDECL(linux_mapoff);
 void NDECL(check_linux_console);