Convert test_mmap to unittest.

Lib/test/output/test_mmap

-test_mmap
-<type 'mmap.mmap'>
-  Position of foo: 1.0 pages
-  Length of file: 2.0 pages
-  Contents of byte 0: '\x00'
-  Contents of first 3 bytes: '\x00\x00\x00'
-
-  Modifying file's content...
-  Contents of byte 0: '3'
-  Contents of first 3 bytes: '3\x00\x00'
-  Contents of second page: '\x00foobar\x00'
-  Regex match on mmap (page start, length of match): 1.0 6
-  Seek to zeroth byte
-  Seek to 42nd byte
-  Seek to last byte
-  Try to seek to negative position...
-  Try to seek beyond end of mmap...
-  Try to seek to negative position...
-  Attempting resize()
-  Creating 10 byte test data file.
-  Opening mmap with access=ACCESS_READ
-  Ensuring that readonly mmap can't be slice assigned.
-  Ensuring that readonly mmap can't be item assigned.
-  Ensuring that readonly mmap can't be write() to.
-  Ensuring that readonly mmap can't be write_byte() to.
-  Ensuring that readonly mmap can't be resized.
-  Opening mmap with size too big
-  Opening mmap with access=ACCESS_WRITE
-  Modifying write-through memory map.
-  Opening mmap with access=ACCESS_COPY
-  Modifying copy-on-write memory map.
-  Ensuring copy-on-write maps cannot be resized.
-  Ensuring invalid access parameter raises exception.
-  Try opening a bad file descriptor...
-  Ensuring that passing 0 as map length sets map size to current file size.
-  Ensuring that passing 0 as map length sets map size to current file size.
-  anonymous mmap.mmap(-1, PAGESIZE)...
- Test passed