License header fixes

Most of the source files had the wrong FSF address. Also reworded the
first paragraph so that licensecheck's regexes actually pick up the
version number.

I made sure lttng.h and lttng-ctl.c advertise LGPL-2.1. Every other file
touched in this patch was and remains under GPL2, please make sure this
is correct. (Some files related to the RCU hashtable are under
LGPL-2.1+, but their headers were already clean).

(closes #155)

Acked-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Signed-off-by: Alexandre Montplaisir <alexandre.montplaisir@gmail.com>
Signed-off-by: David Goulet <dgoulet@efficios.com>