* 12to11.c (XLMain): Initialize primary selections. Transfer
between X and Wayland programs is still incomplete.
* Imakefile (SRCS, OBJS): Add primary selection related objects
and sources.
(primary-selection-unstable-v1.h):
(primary-selection-unstable-v1.c): New targets.
* README: Update what is not supported.
* compositor.h: New prototypes.
* data_device.c (XLDataDeviceSendEnter): Handle resource
allocation failures.
* mime1.awk: Update generated code for changes in target entry
structures.
* seat.c (SetFocusSurface): Handle focus change for primary
selections as well.
(FindSurfaceUnder): Cut off fractional portion instead of
rounding the given coordinates, so the correct surface is found
when the cursor is moved just inside the rightmost pixel.
* surface.c (XLSurfaceRunFrameCallbacks): Handle timestamp
overflow.
* xdata.c (struct _TargetMapping): Rename atom to atom_flag, and
use it to store flags.
(MappingAtom, MappingFlag, MappingIsNextDuplicate, MappingSetFlag)
(MappingUnsetFlag, MappingIs): New macros.
(struct _TargetMappingTable): New structure.
(Duplicate): New definition.
(direct_transfer): Update duplicate types.
(mapping_table): New hash table.
(HashMimeString, SetupMappingTable): New functions.
(FindTranslationForMimeType, Receive): Use the target mapping
table to look up targets instead.
(CheckDuplicate): New function.
(SendOffers): Call CheckDuplicates.
(XLInitXData): Set up duplicate relationship between UTF8_STRING
and is conversion entry, and the targets mapping table.
