prevent rounding 0 if HWTIMER_SPEED > 1000000L

The current macros in hwtimer.h expect HWTIMER_SPEED to be < 1000000L, otherwise integer arithmetic will round the result down to 0.
Add a case to prevent that.
ieee802154: introduce constant for default PAN id
make: allow tagged RIOT_VERSION
doc: added missing closing doxygen brackets
doc: use @brief for single defines
doc: added missing titles
doc: fixed typos and other misspellings
doc: use @false instead of 0
doc: use doxygen li tags
doc: add to group instead of redefining
doc: fix typo in UDP header
doc: remove doxygen duplication
doc: removed broken doxygen struct tags
doc: removed superfluous (and broken) @file params
doc: fixed broken param descriptions
net: socket: fix for e93d030058684f98894aafb5c4048b2c6d9d479f

The former fix for socket initialization was broken. This fixes the
"fix" by using the right exit condition for the loops.
socket: cosmetics
socket: socket_base_exists_socket returns bool

Adapt the prototype to the actual used return value.
cpu: msp430: renamed msp430x16x to msp430fxyz
cpu: lpc2387: integrated lpc_common into lpc2387

Rationale 1: The common part made only sense for (some) NXP ARM7 MCUs,
but was misleading for MCUs like the LPC1768.

Rationale 2: The common part was only used by one specific MCU
implementation - no need to outsource it.