Added experimental 80x40 char VGA controller

Change-Id: I81b73ecb291dc781278ccf89c310d30d18472cd0
Tweaked the clock enable logic to fix some wierdness

Change-Id: I3d112f28ab5f3293f3d19c6ae418d981bb3c1b93
Added initail version of 80 Col OSWRCH

Change-Id: Idb31d40af2f10b639a7f48d44e12b254bb3b9831
OSWRCH80 now working, needed or override OSRDCH to get cursor keys working

Change-Id: If1f645c44cc03b8ddbbe6186838285fac95c90f4
Reworked based on Atom Kernel Source

Change-Id: Ibcefc6dc6ee4924c23f8d2c103d114c95aa4d78e
Started optimising to reduce code size

Change-Id: I35bba965064f455e24f6648611b3b0ecbd826720
More optimisation

Change-Id: Ic780437c0f882014b220609640106ec6f401f60f
First working code for colour attributes

Change-Id: Ic1e5fe91abe8337af6f7d01740fc949174104f38
Fixed left column alignment issue, and also bug in hardware cursor addressing

Change-Id: Ie8aefcf590f91b7912c10d06fa36df156347c59c
Fixed a problem with the cursor position in the right most column

Change-Id: Id25411725535c73ff2055e830d96816fa791514e
Adjusted the write timing to sample the data bus one cycle earlier, as with the IC23 GAL in place writes to the SID were unreliable

Change-Id: I52b89e6b55e61a9f9611ae7e282c1861024c245b
Initial mouse/hardware pointer support, not yet readable from Atom

Change-Id: I0e1886c829253e982d321e33e61619912aaa6888
Mouse/hardware pointer functional and readable from Atom at BDE8,9,A

Change-Id: I32f0f870a1cb76c9f255bd3d8723e328d87f3899
Implemented all 32 pointer styles, based on Kees's samples

Change-Id: I5a7e1072730ccc600258ac3841e02397fe772634
Fixed a couple bugs with the mouse pointer registers

Change-Id: I263d6b56e929f2a36a6ab988133069cf46018570
Added hardware scrolling

Change-Id: Idd0fe4b2d8df6ebff324cf2c4c7d87aa8ea2c63e
Implemented hardware scrolling for vga80 mode; tweaked vga80 timing to match 6847 so that WAIT doesn't get out of step

Change-Id: I6ff2a091a1219da35f24ac05f5f289ab537d310f
Improved horizontal scrolling of vga80x40 so lines wrap onto themselves

Change-Id: Ib74c2ced87c8719d9a861dc1cf096073740ba671
Added left,right,top,bottom margin support to the hardware scrolling

Change-Id: I441be778970127915384f3651c4671d70ca41dd9
Added version register (major.minor) and update #9Fxx addressing to match #BDxx addressing

Change-Id: Ibbd383b2f7fcac82519c172b8a9cef2d17fa2369