add debug statements to lifo
reset unused lifo slots
macro consistency and more DEBUG

addresses https://github.com/RIOT-OS/RIOT/pull/433#discussion_r8437084
add missing debug statement
make reset of freed slots optional

addresses https://github.com/RIOT-OS/RIOT/pull/433#discussion_r8472602
documentation, remove LIFO_DEBUG, break main

add documentation to lifo.h
remove LIFO_DEBUG and use DEVELHELP instead
make the main method which is included break
fix typo, improve doc
Make UART0_BUFSIZE configurable by CPU
Fix coding conventions in uart0.c
Make shell buffer size a shell property
refine DEVELHELP section

more efficient to be better suited for ISR
made testcase more clear
Merge pull request #453 from authmillenon/fix_uart_shell_conflict

Fix uart/shell conflict
Merge pull request #433 from LudwigOrtmann/lifo_debug

lifo debug and reset