Ported the ISA RTC and Memory expansion cards from VARCem's.

Bunch of improvements in the device, memory and MMU handling.
Re-worked the NEAT 286 chipset (ported from VARCem).
Re-worked the ATI 28800 a bit, added Sierra SC1502x ramdac to VGA Wonder XL (Compaq) since it supports such.
Top 384K memory handling improvements (256K top memory too)
Added MCA version of MPU-401 (not tested much, however).
Re-worked the SCAT 286 chipset.

src/isamem.h

@@ -0,0 +1,77 @@
+/*
+ * VARCem	Virtual ARchaeological Computer EMulator.
+ *		An emulator of (mostly) x86-based PC systems and devices,
+ *		using the ISA,EISA,VLB,MCA  and PCI system buses, roughly
+ *		spanning the era between 1981 and 1995.
+ *
+ *		This file is part of the VARCem Project.
+ *
+ *		Definitions for the ISAMEM cards.
+ *
+ * Version:	@(#)isamem.h	1.0.1	2018/08/18
+ *
+ * Authors:	Fred N. van Kempen, <decwiz@yahoo.com>
+ *
+ *		Copyright 2018 Fred N. van Kempen.
+ *
+ *		Redistribution and  use  in source  and binary forms, with
+ *		or  without modification, are permitted  provided that the
+ *		following conditions are met:
+ *
+ *		1. Redistributions of  source  code must retain the entire
+ *		   above notice, this list of conditions and the following
+ *		   disclaimer.
+ *
+ *		2. Redistributions in binary form must reproduce the above
+ *		   copyright  notice,  this list  of  conditions  and  the
+ *		   following disclaimer in  the documentation and/or other
+ *		   materials provided with the distribution.
+ *
+ *		3. Neither the  name of the copyright holder nor the names
+ *		   of  its  contributors may be used to endorse or promote
+ *		   products  derived from  this  software without specific
+ *		   prior written permission.
+ *
+ * THIS SOFTWARE  IS  PROVIDED BY THE  COPYRIGHT  HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND  ANY EXPRESS  OR  IMPLIED  WARRANTIES,  INCLUDING, BUT  NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+ * PARTICULAR PURPOSE  ARE  DISCLAIMED. IN  NO  EVENT  SHALL THE COPYRIGHT
+ * HOLDER OR  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL,  EXEMPLARY,  OR  CONSEQUENTIAL  DAMAGES  (INCLUDING,  BUT  NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE  GOODS OR SERVICES;  LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED  AND ON  ANY
+ * THEORY OF  LIABILITY, WHETHER IN  CONTRACT, STRICT  LIABILITY, OR  TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING  IN ANY  WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+#ifndef ISAMEM_H
+# define ISAMEM_H
+
+
+#define ISAMEM_MAX	4			/* max #cards in system */
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* Global variables. */
+extern const device_t isamem_device;
+extern const device_t isamem_brat80_device;
+extern const device_t isamem_ev159_device;
+
+
+/* Functions. */
+extern void		isamem_reset(void);
+
+extern char	*isamem_get_name(int t);
+extern char	*isamem_get_internal_name(int t);
+extern int	 isamem_get_from_internal_name(char *s);
+extern const device_t	*isamem_get_device(int t);
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif	/*ISAMEM_H*/