Remove cruft, unused files

instant.xml

@@ -1,7 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<instant>
-  <Editor id="12" mixer-width="Wide" zoom-focus="3" zoom="512.000000" snap-to="12" snap-mode="1" edit-point="EditAtPlayhead" playhead="0" show-waveforms="yes" show-waveforms-recording="yes" show-measures="yes" follow-playhead="yes" xfades-visible="yes" region-list-sort-type="ByEndInFile" mouse-mode="MouseObject" show-editor-mixer="yes">
-    <geometry x_size="1242" y_size="768" x_pos="0" y_pos="0" x_off="0" y_off="0" edit_pane_pos="1024"/>
-  </Editor>
-  <Mixer narrow-strips="no" show-mixer="no"/>
-</instant>

libs/pbd/pbd/forkexec.h

@@ -1,30 +0,0 @@
-/*
-    Copyright (C) 2000-2007 Paul Davis
-
-    This program is free software; you can redistribute it and/or modify
-    it under the terms of the GNU General Public License as published by
-    the Free Software Foundation; either version 2 of the License, or
-    (at your option) any later version.
-
-    This program is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-    GNU General Public License for more details.
-
-    You should have received a copy of the GNU General Public License
-    along with this program; if not, write to the Free Software
-    Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
-
-*/
-
-#ifndef __forkexec_h__
-#define __forkexec_h__
-
-#include <unistd.h>
-
-#include "pbd/libpbd_visibility.h"
-
-LIBPBD_API pid_t forkexec(char **argv, char **envp, int outpipe[2], int inpipe[2]);
-LIBPBD_API pid_t forkexec_cmd(char *cmd, char **envp, int outpipe[2], int inpipe[2]);
-
-#endif // __forkexec_h__