Implement VGA memory wrapping for the wrapping line also in vgaonly rendering. Fixes black line in Keen.

git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3859 ed541006-0bf7-43e9-8c4d-6fc63c346d47
Use PCJr specific method to clear the video RAM. Also don't scroll at unspecified video page. Fixes issues with KQ1 and KQ2.

git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3860 ed541006-0bf7-43e9-8c4d-6fc63c346d47
Add Exit conditions for stack over/underflows 
It's bad to continue when these states happen. Let's see if a game triggers it.


git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3861 ed541006-0bf7-43e9-8c4d-6fc63c346d47
lower the influence of the aspect table correction trick when using high scale factors (320x200 =>2000x1200)


git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3862 ed541006-0bf7-43e9-8c4d-6fc63c346d47
Improve the results of the windowed resolution calculation so that the one off errors are gone.
Create a small wrapper function around SDL_SetVideoMode, so that we don't set the same mode twice. 
Both changes benefit people who record footage with external recording software and it speeds up mode video mode changes. (especially with aspect=true)


git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3863 ed541006-0bf7-43e9-8c4d-6fc63c346d47
reordering.

git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3864 ed541006-0bf7-43e9-8c4d-6fc63c346d47
Aspect correct text modes as well.
I hope I got the ratios right. Let me know if I messed up.

git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3865 ed541006-0bf7-43e9-8c4d-6fc63c346d47
25*14=350

git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3866 ed541006-0bf7-43e9-8c4d-6fc63c346d47
the mapper needs to use the wrapper as well.


git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3867 ed541006-0bf7-43e9-8c4d-6fc63c346d47
Illegal memory reads have all bits set. Fixes early (and buggy) shareware versions of Shadow Warrior.

git-svn-id: http://svn.code.sf.net/p/dosbox/code-0/dosbox/trunk@3868 ed541006-0bf7-43e9-8c4d-6fc63c346d47