liblog: logcat: colored output.

This patch adds a new '-v color' option to logcat so that the output is
colored similar to the ones in DDMS. Simply type "adb logcat -v color"
to use it. Works well with bash in gnome-terminal. NO GUARANTEE IT WILL
WORK ON A NON xterm STYLE TERMINAL.

Signed-off-by: Michael Zimmermann <sigmaepsilon92@gmail.com>
Signed-off-by: Mark Salyzyn <salyzyn@google.com>
Change-Id: I9189c5f27fed991579edbcbc6834536eb8112152