Boost unit-testing framework.

make -f makefile.{unix,osx,mingw} test_bitcoin
to compile dumb, do-almost-nothing placeholder unit tests.

src/test/README

@@ -0,0 +1,21 @@
+The sources in this directory are unit test cases.  Boost includes a
+unit testing framework, and since bitcoin already uses boost, it makes
+sense to simply use this framework rather than require developers to
+configure some other framework (we want as few impediments to creating
+unit tests as possible).
+
+The build system is setup to compile an executable called "test_bitcoin"
+that runs all of the unit tests.  The main source file is called
+test_bitcoin.cpp, which simply includes other files that contain the
+actual unit tests (outside of a couple required preprocessor
+directives).  The pattern is to create one test file for each class or
+source file for which you want to create unit tests.  The file naming
+convention is "<source_filename>_tests.cpp" and such files should wrap
+their tests in a test suite called "<source_filename>_tests".  For an
+examples of this pattern, examine uint160_tests.cpp and
+uint256_tests.cpp.
+
+For further reading, I found the following website to be helpful in
+explaining how the boost unit test framework works:
+
+http://www.alittlemadness.com/2009/03/31/c-unit-testing-with-boosttest/