Consistently use curly braces instead of parentheses in makefiles.
Use $(MAKE) instead of naked make.
GNU make may be named differently on some platforms, e.g., gmake.
Relax compiler warnings for FreeBSD.
FreeBSD has both ancient GCC 4.2 and brand new Clang 3.3.
Fix compiler warnings for GCC 4.2.
These changes work around warnings caused by "-Wbad-function-cast".