Do not include parser-defs.h from c-lang.h

While working on another series, I noticed that c-lang.h does not need
to include parser-defs.h.  This patch makes this change, and fixes up
the two .c files that needed this include.  Tested by rebuilding.

gdb/ChangeLog
2020-11-25  Tom Tromey  <tom@tromey.com>

	* d-lang.c: Include parser-defs.h.
	* rust-lang.c: Include parser-defs.h.
	* c-lang.h: Do not include parser-defs.h.

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2020-11-25  Tom Tromey  <tom@tromey.com>
+
+	* d-lang.c: Include parser-defs.h.
+	* rust-lang.c: Include parser-defs.h.
+	* c-lang.h: Do not include parser-defs.h.
+
 2020-11-24  Simon Marchi  <simon.marchi@polymtl.ca>
 
 	* regcache.h (struct cached_reg): Remove typedef.

gdb/c-lang.h

@@ -28,7 +28,6 @@ struct parser_state;
 
 #include "value.h"
 #include "macroexp.h"
-#include "parser-defs.h"
 #include "gdbsupport/enum-flags.h"
 
 

gdb/d-lang.c

@@ -26,6 +26,7 @@
 #include "demangle.h"
 #include "cp-support.h"
 #include "gdbarch.h"
+#include "parser-defs.h"
 
 /* The name of the symbol to use to get the name of the main subprogram.  */
 static const char D_MAIN[] = "D main";

gdb/rust-lang.c

@@ -38,6 +38,7 @@
 #include <string>
 #include <vector>
 #include "cli/cli-style.h"
+#include "parser-defs.h"
 
 /* See rust-lang.h.  */