imlib2: Update graphics/imlib to 1.5.1

pkgsrc changes:
- Remove lround patches: lround is no longer used
- Remove #ifndef blocks to rip out XShm support.  Unfortunately
  the logic is much more convoluted now and #ifndef parts of the code
  no longer scale.
  Please note that this can break support on Interix!

Changes:
1.5.1
*****
Kim Woelders (13):
- Fix build without HAVE_X11_SHM_FD (T6752)
- XPM loader: Fix potential use of uninitialized value (T6746)
- BMP loader: Fix infinite loop with invalid bmp images (T6749)
- PNM loader: Simplify (fixing ASCII format parsing issues T6751)
- BMP loader: Fix warnings found with -O3
- Maximum image dimension should be 32767, not 32766
- PNG loader: Correct various error handling cases
- Add missing const to imlib_apply_filter() script argument
- Warning fixes in imlib2_... programs
- imlib2_view: Limit window dimensions to 32767
- grab.c: Fix gcc8 warning
- imlib2_conv.c: Fix gcc8 warning
- 1.5.1.

1.5.0
*****
Alexander Volkov (3):
- put a check for shared memory inside __imlib_ShmGetXImage()
- introduce __imlib_ShmDestroyXImage() instead of __imlib_ShmDetach()
- Add support for MIT-SHM FD-passing

Kim Woelders (19):
- XPM loader: Fix incorrect image invalidation.
- Make some more functions static.
- Introduce __imlib_LoadImageData()
- Remove redundant CAST_IMAGE()
- imlib2_grab: Always use imlib_create_scaled_image_from_drawable() to grab image
- imlib_create_scaled_image_from_drawable(): speed up 1:1 case
- imlib_create_scaled_image_from_drawable(): Drop shape handling if unshaped
- Indent
- Autofoo cosmetics
- Strip trailing whitespace, cosmetics
- Fix potential OOB memory access if border elements are negative
- Fix potential OOB memory access if border sizes exceed image dimensions
- Introduce IMLIB2_SHM_OPT to enable overriding/testing SHM modes
- Add IMLIB2_XIMAGE_CACHE_COUNT to enable testing the ximage cache
- Refactor the XImage cache
- Add imlib_get_cache_used()
- Expose XImage cache control functions
- Drop -Waggregate-return
- 1.5.0.

(leot)