Main fixes

some fixes to the main branch
especially important is the ability to include a config.mak

mine for example contains:

CFLAGS += -I /usr/local/include -g3 -O0 
#CFLAGS += -fsanitize=address
LDFLAGS += -L /usr/local/lib -Wl,--rpath=/usr/local/lib
CXXFLAGS += -g3 -O0
#CXX = fasan
#CC = fasan