build: update compile.sh to support bsd systems
build: switch from hardcoded gcc to default c compiler

On FreeBSD /usr used by base system, use PREFIX=/usr/local instead.
On BSD systems gnu "make" has the name "gmake".

	modified:   Makefile
	modified:   compile.sh

Signed-off-by: Oliver Pinter <op@crysys.hu>
build: switch from hardcoded gcc to default c compiler

	modified:   tests/Makefile

Signed-off-by: Oliver Pinter <op@crysys.hu>
info: update COMPILE.TXT related to bsd target

	modified:    COMPILE.TXT

Signed-off-by: Oliver Pinter <op@crysys.hu>