add stepper fail count (for force position movement)
modified:   Makefile: upgrade version to v0.2.1 .
modified:   VERSION: version v0.2.1 .
modified:   stepper.h: add fail count member and increment it in move fonctions in stepper with reader class.
modified:   stepper.help.output: automatic update.
small change in g++ command line for gcc v4.7 .
modified:   Makefile: swap source and library on command line (for ld error on gcc v4.7 ).
modified:   stepper.help.output: auto updated.