Better build support for custom baudrates

For some systems (OSes, versions, architectures) custom-baudrate
support is enabled by default.

For others, support may work, but must be enabled by defining
USE_CUSTOM_BAUD in the Makefile

You can also disable custom baudrate support altogether (even for
systems where it's enabled by default), by defining NO_CUSTOM_BAUD in
the Makefile

custbaud.h

@@ -0,0 +1,75 @@
+/* vi: set sw=4 ts=4:
+ *
+ * custbaud.h
+ *
+ * Automatically enable custom baudrate support for systems (OS /
+ * version / architecture combinations) we know it works.
+ *
+ * by Nick Patavalis (npat@inaccessnetworks.com)
+ *
+ * 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ * USA
+ */
+
+#ifndef CUSTBAUD_H
+#define CUSTBAUD_H
+
+#ifndef NO_CUSTOM_BAUD
+
+#if defined (__linux__)
+
+#include <linux/version.h>
+#if LINUX_VERSION_CODE > KERNEL_VERSION(2,6,0)
+#if defined (__x86__) || defined (__x86_64__) || defined (USE_CUSTOM_BAUD)
+#ifndef USE_CUSTOM_BAUD
+#define USE_CUSTOM_BAUD
+#endif
+#define CUSTOM_BAUD_HEAD "termios2.h"
+#endif /* of arch */
+#endif /* of version */
+
+#elif defined (__FreeBSD__) || defined (__OpenBSD__) || \
+      defined (__DragonFly__) || defined (__APPLE__)
+
+#ifndef USE_CUSTOM_BAUD
+#define USE_CUSTOM_BAUD
+#endif
+#define CUSTOM_BAUD_HEAD "custbaud_bsd.h"
+
+#elif defined (USE_CUSTOM_BAUD)
+
+#error "USE_CUSTOM_BAUD not supported on this system!"
+
+#endif /* of platforms */
+
+#else /* of ndef NO_CUSTOM_BAUD */
+
+#ifdef USE_CUSTOM_BAUD
+#undef USE_CUSTOM_BAUD
+#endif
+
+#endif /* of ndef NO_CUSTOM_BAUD else */
+
+#endif /* CUSTBAUD_H */
+
+/**************************************************************************/
+
+/*
+ * Local Variables:
+ * mode:c
+ * tab-width: 4
+ * c-basic-offset: 4
+ * End:
+ */