Move interpreter_p declaration to main.h

This moves the interpreter_p declaration from defs.h to main.h.  I
think this makes more sense, as it is defined in main.c.  Also, this
declaration was in the wrong place -- between a comment and the things
the comment described.

gdb/ChangeLog
2019-05-08  Tom Tromey  <tromey@adacore.com>

	* tui/tui-interp.c: Include main.h.
	* interps.c: Include main.h.
	* main.h (interpreter_p): Declare.
	* defs.h (interpreter_p): Don't declare.

gdb/ChangeLog

@@ -1,3 +1,10 @@
+2019-05-08  Tom Tromey  <tromey@adacore.com>
+
+	* tui/tui-interp.c: Include main.h.
+	* interps.c: Include main.h.
+	* main.h (interpreter_p): Declare.
+	* defs.h (interpreter_p): Don't declare.
+
 2019-05-08  Tom Tromey  <tromey@adacore.com>
 
 	* dwarf2loc.c: Include dwarf2read.h.

gdb/defs.h

@@ -584,9 +584,6 @@ extern int watchdog;
 
 /* Hooks for alternate command interfaces.  */
 
-/* * The name of the interpreter if specified on the command line.  */
-extern char *interpreter_p;
-
 struct target_waitstatus;
 struct cmd_list_element;
 

gdb/interps.c

@@ -38,6 +38,7 @@
 #include "completer.h"
 #include "top.h"		/* For command_loop.  */
 #include "continuations.h"
+#include "main.h"
 
 /* Each UI has its own independent set of interpreters.  */
 

gdb/main.h

@@ -35,6 +35,9 @@ extern int return_child_result_value;
 extern int batch_silent;
 extern int batch_flag;
 
+/* * The name of the interpreter if specified on the command line.  */
+extern char *interpreter_p;
+
 /* From mingw-hdep.c, used by main.c.  */
 
 /* Return argv[0] in absolute form, if possible, or ARGV0 if not.  The

gdb/tui/tui-interp.c

@@ -34,6 +34,7 @@
 #include "observable.h"
 #include "gdbthread.h"
 #include "inferior.h"
+#include "main.h"
 
 /* Set to 1 when the TUI mode must be activated when we first start
    gdb.  */