environment variables handling. Replaced that with three per-bitmap
functions: cucul_set_bitmap_antialias(), cucul_set_bitmap_color() and
cucul_set_bitmap_dithering().
* Added cucul_set_bitmap_brightness() and cucul_set_bitmap_contrast()
prototypes (but did not implement them yet).
* Added cucul_set_bitmap_charset() to choose what characters are going
to be used for the bitmap rendering.
* Removed the now useless cucul_get_feature(), cucul_set_feature() etc.
* Got rid of static buffers; we now use cucul_free() to free exported
buffers.
* Fixed light background in the ANSI exporter by adding escape sequences for
most terminal emulators.
+ Changed port to 51914 (rationale: it's 0xCACA; so okay, it's outside
the registered ports area, but we'd never be accepted anyway).
+ Retry network sends in caca_get_event(), too.
+ Have a per-client buffer in case of network congestion. If that buffer
gets full, just drop it and start again at the next frame.
+ Set the window title to "caca for the network".
+ Do not send the ANSI buffer's terminating \0.
+ Restore the SIGPIPE handler on close.
+ Set window size to 80x24 instead of 80x25.