configure test for boost_thread fails link on OSX (Darwin 11.4)

In drizzle-7.2.3, compiling from source on
MacOSX 10.7.5 (Lion), using
Xcode 4.5.2 (i686-apple-darwin11-llvm-gcc-4.2 (GCC) 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.1.00)), and
boost-1.52 from MacPorts,

The configure test for boost_thread-mt fails because linkage of conftest fails, because use of boost_thread-mt requires linkage of boost_system-mt.

Changing the AC_LIB_HAVE_LINKFLAGS call for boost_thread-mt (in m4/pandora_have_libboost_thread.m4) to include boost_system-mt as a dependency (as per the attached patch) solves the problem.

Problem (CFLAGS/LDFLAGS used to find dependencies via MacPorts):

./configure --prefix=/platform/stow/drizzle-7.2.3 CFLAGS=-I/opt/local/include LDFLAGS=-L/opt/local/lib
<...>
checking how to link with libboost_program_options-mt... -lboost_program_options-mt
checking for libc... (cached) no
checking for libboost_thread-mt... no
checking for libboost_thread... no
configure: error: boost::thread is required for drizzle

From config.log:

configure:34836: g++ -o conftest -D_THREAD_SAFE -D_THREAD_SAFE -isystem /opt/local/include -I/opt/local/include -L/opt/local/lib conftest.cpp -lintl -lboost_thread-mt >&5
Undefined symbols for architecture x86_64:
  "boost::system::generic_category()", referenced from:
      __static_initialization_and_destruction_0(int, int)in ccW6zDIM.o
  "boost::system::system_category()", referenced from:
      __static_initialization_and_destruction_0(int, int)in ccW6zDIM.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status
configure:34836: $? = 1

See attached patch, which just adds this library to the dependencies. You might want to check for its existence, etc, first, if you wish to maintain the ability to specify locations for each of the boost libraries separately.