- Copy stable/10@296371 to releng/10.3 in preparation for 10.3-RC1
builds.
- Update newvers.sh to reflect RC1.
- Update __FreeBSD_version to reflect 10.3.
- Update default pkg(8) configuration to use the quarterly branch.

Approved by: re (implicit)

MFC r280950: Move the efi loaders to be under sys/boot/efi

In HEAD this was done to support UEFI on arm64. Merging to stable/10 to
facilitate the merging of later UEFI changes.