Still fixing the unittests...

Still fixing the unittests...

- Fix argument order in ASSERT_EQUALS

  For a few tests the order of the arguments of ASSERT_EQUALS were swapped.
  Although it did not cause problems beacuse of the commutative nature of the
  equality operator, if such a test failed the reported error was incorrect
  and misleading.

  Also removed a duplicate test.

- Fix an unused parameter warning

- Fix unittest compilation with Boost enabled

- Fix check for '%e' conversion

  The documentation says only that the exponent is at least two digits, not that
  it is exactly two digits. It depends on the underlying C Runtime Library how
  many digits are used.

  The check itself is meant only to check if a wrong type argument is accepted
  and handled as if it was a matching type, and it still fulfills that
  requirement.

- Ensure we can read the source directory

  By checking early for the existence and readability of the source directory
  we can provide a different failure message from when the actual file I/O
  check fail.

  There are systems where the compiler's handling of non-ASCII characters is
  different from the OS's way. In such a system this test will fail if the
  source directory name contains non-ASCII characters.

- The order does matter, #2

  For some linker the order of the libraries on the command-line does matter.