Split BOOSTDIR into BOOSTDIR_BASEDIR and BOOSTDIR_BASENAME (optionally).

This is to give us a way to let which boost to use toggleable in the
source code as BOOSTDIR_BASENAME, and let build enviornments configure
where to find appropriately named boost folders via BOOSTDIR_BASEDIR.

This isn't pretty, and CMake's FindBoost is a far better way to do this,
but it'll work for now.

Makefile

@@ -36,6 +36,7 @@ ifeq ($(NIGHTLY),true)
 	CFLAGS += -DFDB_CLEAN_BUILD
 endif
 
+BOOST_BASENAME ?= boost_1_52_0
 ifeq ($(PLATFORM),Linux)
   PLATFORM := linux
 
@@ -44,7 +45,7 @@ ifeq ($(PLATFORM),Linux)
 
   CXXFLAGS += -std=c++0x
 
-  BOOSTDIR ?= /opt/boost_1_52_0
+  BOOST_BASEDIR ?= /opt
   TLS_LIBDIR ?= /usr/local/lib
   DLEXT := so
   java_DLEXT := so
@@ -60,15 +61,14 @@ else ifeq ($(PLATFORM),Darwin)
 
   .LIBPATTERNS := lib%.dylib lib%.a
 
-  BOOSTDIR ?= $(HOME)/boost_1_52_0
-  CXXFLAGS += -D BOOST_ASIO_HAS_STD_ARRAY # TODO: Remove this after Boost upgrades to 1.67
-
+  BOOST_BASEDIR ?= ${HOME}
   TLS_LIBDIR ?= /usr/local/lib
   DLEXT := dylib
   java_DLEXT := jnilib
 else
   $(error Not prepared to compile on platform $(PLATFORM))
 endif
+BOOSTDIR ?= ${BOOST_BASEDIR}/${BOOST_BASENAME}
 
 CCACHE := $(shell which ccache)
 ifneq ($(CCACHE),)