[CMD] GOTO: Fix label parsing.

We note two things, when CMD searches for the corresponding label in the
batch file:
- the first character of the line is always ignored, unless it's a colon;
- the escape caret ^ is supported and interpreted.

Fixes some cmd_winetests.

base/shell/cmd/cmd.h

@@ -301,6 +301,10 @@ INT cmd_move (LPTSTR);
 INT CommandMsgbox (LPTSTR);
 
 /* Prototypes from PARSER.C */
+
+/* These three characters act like spaces to the parser in most contexts */
+#define STANDARD_SEPS _T(",;=")
+
 enum { C_COMMAND, C_QUIET, C_BLOCK, C_MULTI, C_OR, C_AND, C_PIPE, C_IF, C_FOR };
 typedef struct _PARSED_COMMAND
 {