Makefiles: src recompile/efficiency

[bdsullivan]

Update makefiles to avoid recompiling all source files for each executable e.g.:

MAD_WIS_SRC = ./src/MadnessTableProcessor.cpp ./src/mad_main.cpp ./src/weighted_ind_set.cpp src/PTD.cpp
madwis: $(SHAREDOBJ)

$(CC) $(CFLAGS) $(MAD_WIS_SRC) $(SHAREDOBJ) $(INC_DIR) $(LIB_DIR) $(LIBS) -o $(MAD_WIS_EXE)

becomes
MAD_WIS_OBJ = ./src/MadnessTableProcessor.o ./src/mad_main.o ./src/weighted_ind_set.o src/PTD.o

madwis: $(SHAREDOBJ) $(MAD_WIS_OBJ)

$(CC) $(CFLAGS) $(MAD_WIS_OBJ) $(SHAREDOBJ) $(INC_DIR) $(LIB_DIR) $(LIBS) -o $(MAD_WIS_EXE)