Move definitions to fix 26 errors which adds new translatable strings

Fixes the following 26 errors when generating a translation file with e.g. "make de.ts":
/home/daniel/Lmms/plugins/monstro/Monstro.h:69: tr() cannot be called without context
/home/daniel/Lmms/plugins/monstro/Monstro.h:70: tr() cannot be called without context
...
/home/daniel/Lmms/plugins/monstro/Monstro.h:96: tr() cannot be called without context
/home/daniel/Lmms/plugins/monstro/Monstro.h:97: tr() cannot be called without context