dotted line pattern support

[stevesims]

Canvas gets several new calls:

setLinePattern accepts a LinePattern object for setting a pattern a line can optionally use

setLinePatternLength allows the length of the line pattern to be set

setLinePatternOffset allows the offset within the pattern to be adjusted

setLineOptions sets whether a line should be drawn as a dotted line, and whether its first and/or last points should be omitted

BitmappedDisplayController’s PaintState object now includes linePattern, lineOptions and linePatternLength.

genericAbsDrawLine now looks at the lineOptions in the current paint state to determine whether a dotted line should be drawn, and whether first or last points should be omitted

fabutils gains a getBit function which will get a bit at an index within an array of uint8_t numbers. the position is in “most significant bit” order, i.e. bitIndex 0 is the bit representing 128 in the first byte in the array

[stevesims]

Adds support for dotted lines plotting, essentially as per Acorn's dot-dash line plotting whereby a pattern of 1-64 bits in length can be applied to a line

this will be used and form part of the next release of the console8 agon-vdp (2.7.0)