Rework directory structure to use GNU-recommended "src" directory.

Move the source code (other than glob) into the "src" subdirectory.
Update all scripting and recommendations to support this change.

* *.c, *.h, w32/*: Move to src/
* configure.ac, Makefile.am, maintMakefile: Locate new source files.
* Basic.mk.template, mk/*: Update for new source file locations.
* NEWS, README.DOS.template: Update for new locations.
* build.template, build_w32.bat, builddos.bat: Ditto.
* po/POTFILES.in: Ditto
* tests/run_make_tests.pl, tests/scripts/features/load*: Ditto.
* make.1: Move to doc.
* mk/VMS.mk: Add support for building on VMS (hopefully).
* makefile.vms, prepare_w32.bat: Remove.
* SCOPTIONS: Update to define HAVE_CONFIG_H

src/debug.h

@@ -0,0 +1,39 @@
+/* Debugging macros and interface.
+Copyright (C) 1999-2017 Free Software Foundation, Inc.
+This file is part of GNU Make.
+
+GNU Make 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 3 of the License, or (at your option) any later
+version.
+
+GNU Make 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, see <http://www.gnu.org/licenses/>.  */
+
+#define DB_NONE         (0x000)
+#define DB_BASIC        (0x001)
+#define DB_VERBOSE      (0x002)
+#define DB_JOBS         (0x004)
+#define DB_IMPLICIT     (0x008)
+#define DB_MAKEFILES    (0x100)
+
+#define DB_ALL          (0xfff)
+
+extern int db_level;
+
+#define ISDB(_l)    ((_l)&db_level)
+
+/* When adding macros to this list be sure to update the value of
+   XGETTEXT_OPTIONS in the po/Makevars file.  */
+#define DBS(_l,_x)  do{ if(ISDB(_l)) {print_spaces (depth); \
+                                      printf _x; fflush (stdout);} }while(0)
+
+#define DBF(_l,_x)  do{ if(ISDB(_l)) {print_spaces (depth); \
+                                      printf (_x, file->name); \
+                                      fflush (stdout);} }while(0)
+
+#define DB(_l,_x)   do{ if(ISDB(_l)) {printf _x; fflush (stdout);} }while(0)