optimize by merging cells

cells on any row of the table then the very first row does not use the
cell-merging optimization; this appears to fix the last of the table
layout bugs seen in truecolor.php; also fix the foreground and
background color bugs seen in truecolor.php.

get hopelessly lost.

are almost there.

split is rendered moot by the plugin system: when enabled, binaries do
not link directly with libX11 or libGL. I hope this is a step towards
more consisteny and clarity.

* Better CFLAGS and LDFLAGS propagation to the Makefiles.

documented).

far better for error checking.

* Use size_t and ssize_t where appropriate.

completely breaks compatibility with previous versions of libcaca on
    64-bit systems.

prototypes. As they are equivalent, this does not break the ABI.

<cucul.h> will provide the C99 types, even if libcaca has been installed.
  * Rename what's left of "common.h" to "stubs.h".
  * Remove all references to erroneous <inttypes.h> from source files.

applications. I'll think of a migration path later.

if they modified it.

* Free the internal font when closing the GL driver.
  * Hide the window when closing the GL driver, because freeglut's
    glutDestroyWindow() does not really closes the window.

lead to deadlocks.

without using environment variables..
  * Implement caca_get_display_driver() to return the current display's
    output driver.
  * Add a simple example program to test caca_create_display_with_driver().

major/minor computation scheme.