Translates SGR control sequences into overlays or extents.
Delete all other control sequences without processing them.
SGR control sequences are applied by calling the function
specified by `ansi-color-apply-face-function'. The default
function sets foreground and background colors to the text
between BEGIN and END, using overlays. The colors used are given
in `ansi-color-faces-vector' and `ansi-color-names-vector'. See
`ansi-color-apply-sequence' for details.
Every call to this function will set and use the buffer-local
variable `ansi-color-context-region' to save position and current
ansi codes. This information will be used for the next call to
`ansi-color-apply-on-region'. Specifically, it will override
BEGIN, the start of the region and set the face with which to
start. Set `ansi-color-context-region' to nil if you don't want this.