- add tommath_private.h to HEADERS
- only install public header files
- move more shared stuff to makefile.include
- make it possible to override the *PATH makefile variables
to be used in makefile and makefile.shared
use -Wextra instead of deprecated -W
add additional warnings also used in libtomcrypt
can be disabled by defining NO_ADDTL_WARNINGS
add possibility to define COMPILE_SIZE or COMPILE_DEBUG