* dtable.cc: Mark some const variables as static.

* environ.cc (conv_start_chars): Move to shared cygwin region and initialize at
compile time.
(match_first_char): New generic function for querying conv_start_chars.
(posify_maybe): Rename from posify.
(environ_init): Remove conv_envvars initialization.  Don't check
conv_start_chars, just allow posify_maybe to make the decision.
* fhandler_console.cc (__vt100_conv): Fix formatting.  Mark as const.

winsup/cygwin/fhandler_console.cc

@@ -1208,7 +1208,7 @@ fhandler_console::cursor_get (int *x, int *y)
 
 /* VT100 line drawing graphics mode maps `abcdefghijklmnopqrstuvwxyz{|}~ to
    graphical characters */
-static wchar_t __vt100_conv [31] = {
+static const wchar_t __vt100_conv[31] = {
 	0x25C6, /* Black Diamond */
 	0x2592, /* Medium Shade */
 	0x2409, /* Symbol for Horizontal Tabulation */