first changes for atari5200 target
add get_tv()
add some conio functions
use __RESERVED_MEMORY__ to reserve memory for the default 20x24 text screen
add gotox, gotoy, and gotoxy
Merge remote-tracking branch 'upstream/master' into a5200
initial version of a P/M mouse callback
- always use page 6 for P/M mouse cursor
- make cursor character of text mode callback configurable
- change default cursor character of text mode callback from 'plus' to 'diamond'
- set P/M callback as default
address issue raised in the pull request; add support to not use page 6
again
Fixed typos.  And, fixed descriptions of where ld65 looks for files.
Selection whether to use page 6 for mouse P/M data is not done in
Makefile.inc, like the other compile-time options. Small fix in the
P/M mouse "show" routine: adapt mouse cursor colors to current
screen colors.
Merge pull request #106 from groessler/something_to_pull

add P/M (aka 'Sprite') mouse callback for Atari
Merge pull request #110 from greg-king5/typo

Fixed typos; and, fixed descriptions of where ld65 looks for files.
Put mouse cursor shape definition into .rodata.
Document mouse callbacks and some other small changes.
Merge pull request #111 from groessler/something_to_pull

Document Atari mouse callbacks
Avoided makeinfo warnings when Travis CI runs LinuxDoc Tools.
Merge remote-tracking branch 'upstream/master' into a5200
atari5200 update: simple conio "hello world" works now
Avoided some makeinfo warnings when Cygwin runs LinuxDoc Tools.