Strip unnecessary extern keywords from header files

git-svn-id: https://subversion.ews.illinois.edu/svn/sp14-ece391/_projects/group14/branches/terminal-driver@15231 1cec0ab5-dbbe-4d55-bb2a-e14ca091d7d0
Move some VGA-specific variables and routines to the VGA-specific files

git-svn-id: https://subversion.ews.illinois.edu/svn/sp14-ece391/_projects/group14/branches/terminal-driver@15232 1cec0ab5-dbbe-4d55-bb2a-e14ca091d7d0
Add skeleton for terminal driver support

git-svn-id: https://subversion.ews.illinois.edu/svn/sp14-ece391/_projects/group14/branches/terminal-driver@15233 1cec0ab5-dbbe-4d55-bb2a-e14ca091d7d0