* Add os specific sed for FreeBSD.
* Replace hardcoded "make" with $(MAKE)
Some systems don't use GNU make by default, and use something like
gnumake or gmake. Respect that when determining the make version.
This allows the user to specify build flags from the make command
line. For example to force a complete rebuild one could use:
make BUILD_FLAGS='-v -a' TAGS="sqlite"
dankm