amalgamated build concatenates all files into a single .c file to
allow compiler see all symbols and produce possibly smaller code.
for binary distributions this is what you want, as it's faster but
may consume more memory during compilation.
it however cannot do incremental builds.

the current Go doesn’t support c-shared on other architectures than amd64

same for LDFLAGS. this fixes common problem where CFLAGS after make
was evaluated as a make variable and replaced the default, while
before as env variable and was prepended to the default string.
now they both behave as an env. variable

the Redis backend supports UNIX, TCP and custom ports
no real transactions nor iteration, but it’s not needed at the moment
transactions keep replies in a freelist, which is purged on transaction
commit / abort

memcached is a distributed caching system, it is a good fit
for building resolvers with shared and replicated cache

On FreeBSD the lua package was not detected. (Tested on 9.3 and 10.1).

the build system now doesn't always relink targets

This reverts commit 17fd0612.

This reverts commit 17fd0612.