Fixed __SET_EXTERNAL_FB declaration in accessor.h, invoked when accessing EXTERNAL_BLOCK.VARIABLE. Macro was invoking __SET_VAR with wrong parameter count. Fixed corresponding code generator for ST. Seems similar codegen for IL is also broken, but fix would affect other (unknown) behviours -> didn't touch it.

AM_CXXFLAGS = -g -Wall -Wpointer-arith -Wwrite-strings -Wno-unused