bump to 0.55:

bump to 0.55:

This is primarily a bug fix release.

Note: Test::More is now a pre-requisite for Imager and is no longer
bundled.

There is one new feature:

- the Win32 font driver now supports UTF8 (RT 22166)

Several bugs were fixed:

- the string() method would not output the string "0" (RT 21770)

- fills.c was failing to compile on Solaris 10 (compiler unknown) (RT 21944)

- the gif_disposal and gif_user_input tags weren't being read from the file
  correctly (RT 22192)

- Win32 font driver fixes:
  - the global descent value from bounding box was the wrong sign
  - if the first or last glyph overflowed the left or right side of
    the advance width they would be clipped

- gif.c was failing to build under MSVC (RT 23922)

- in some cases strings passed to the string() method were treated as
  terminated by NUL (chr 0) (RT 21770)

- on "MSWin32" perl builds we now link to -lzlib instead of -lz since
  that's the default build name for zlib on Win32. (RT 23064)

- search $Config{incpath} for headers too, which we should have been
  doing all along.