Move low-level hardware writing from output.c to new file hw/serialio.c.

Avoid hardware specific code in output.c.  This will reduce the amount
of change needed to output.c as support for more serial hardware is
added.

This patch also renames some functions to improve the naming scheme.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
diff --git a/Makefile b/Makefile
index 855fdf4..e39222b 100644
--- a/Makefile
+++ b/Makefile
@@ -29,7 +29,7 @@
 SRCBOTH=misc.c stacks.c output.c string.c x86.c block.c cdrom.c mouse.c kbd.c \
     serial.c clock.c resume.c pnpbios.c vgahooks.c pcibios.c apm.c \
     fw/smp.c \
-    hw/pci.c hw/timer.c hw/rtc.c hw/dma.c hw/pic.c hw/ps2port.c \
+    hw/pci.c hw/timer.c hw/rtc.c hw/dma.c hw/pic.c hw/ps2port.c hw/serialio.c \
     hw/usb.c hw/usb-uhci.c hw/usb-ohci.c hw/usb-ehci.c hw/usb-xhci.c \
     hw/usb-hid.c hw/usb-msc.c hw/usb-uas.c \
     hw/blockcmd.c hw/floppy.c hw/ata.c hw/ramdisk.c \
@@ -201,7 +201,7 @@
 ################ VGA build rules
 
 # VGA src files
-SRCVGA=src/output.c src/string.c src/hw/pci.c \
+SRCVGA=src/output.c src/string.c src/hw/pci.c src/hw/serialio.c \
     vgasrc/vgabios.c vgasrc/vgafb.c vgasrc/vgafonts.c vgasrc/vbe.c \
     vgasrc/stdvga.c vgasrc/stdvgamodes.c vgasrc/stdvgaio.c \
     vgasrc/clext.c vgasrc/bochsvga.c vgasrc/geodevga.c