Add the Epson Equity LT Machine

This is a portable computer based around NEC V30 processor and what
seems to be a proprietary Epson chip set.

The chip set provides a XT-class keyboard controller/PPI, controller for
two DD floppy drives, CGA-compatible video, one serial and one parallel
port. There's no datasheet for the chip set.

The machine has a 640x200 monochromatic LCD display, optionally backlit
and an external CRT connector. There can be up to two floppy drives,
one of them optionally connected to an external connector (shared with
the parallel port). There are physical switches to enable the external
CRT and floppy connectors.

There's a battery-backed RTC/NVRAM that holds configuration, including
backlight timeout, UART configuration and floppy types.

The machine has two expansion slots, half the pich of a regular 8-bit
ISA, but electrically compatible. Hard drive and modem adapters were
available, I don't have them.

The checksums of the ROM images are as follows:

  SHA1(2d58397f81f006e7729648dd3720e3004e20ac36) =
  roms/machines/elt/HLO-B2.rom

  SHA1(8c06cd3905f71f15fec2a3759cea5b2c5dc602c3) =
  roms/machines/elt/HLO-A2.rom

src/machine/machine_table.c

@@ -2117,6 +2117,42 @@ const machine_t machines[] = {
         .snd_device = NULL,
         .net_device = NULL
     },
+    {
+        .name = "[8086] Epson Equity LT",
+        .internal_name = "elt",
+        .type = MACHINE_TYPE_8086,
+        .chipset = MACHINE_CHIPSET_PROPRIETARY,
+        .init = machine_elt_init,
+        .pad = 0,
+        .pad0 = 0,
+        .pad1 = MACHINE_AVAILABLE,
+        .pad2 = 0,
+        .cpu = {
+            .package = CPU_PKG_8086,
+            .block = CPU_BLOCK_NONE,
+            .min_bus = 0,
+            .max_bus = 0,
+            .min_voltage = 0,
+            .max_voltage = 0,
+            .min_multi = 0,
+            .max_multi = 0
+        },
+        .bus_flags = MACHINE_PC,
+        .flags = MACHINE_VIDEO,
+        .ram = {
+            .min = 640,
+            .max = 640,
+            .step = 640
+        },
+        .nvrmask = 0x3f,
+        .kbc = KBC_IBM_PC_XT,
+        .kbc_p1 = 0xff00,
+        .gpio = 0xffffffff,
+        .device = NULL,
+        .vid_device = NULL,
+        .snd_device = NULL,
+        .net_device = NULL
+    },
 
 #if defined(DEV_BRANCH) && defined(USE_LASERXT)
     {