MFC Loader Fixes 2017q2: r316437,r316577,r316578,r316585,r316590,r316612,
r316625,r316628,r316654,r316682,r316704,r316771,r317092,r317097,r317099,
r317652,r317785,r317886,r317887,r318142,r318320,r318356,r318678,r318754,
r318982,r318986,r318987,r318988,r318989,r318990,r318991,r318992,r318993,
r318994,r318999,r319083,r319084,r319085,r320011,r320234,r320288,r320304,
r320467,r320482

r316437: Small cleanup to make i386/loader match efi/loader boot environment
code

r316577: loader: part.c cstyle cleanup

r316578: loader: want mechanism to avoid RA with bcache

r316585: loader: zfs reader should check all labels

r316590: libstand/dosfs: cache FAT32 in 128 Kb blocks to save loader memory

r316612: In r298230 the value of HEAP_MIN was changed from 3MB to 64MB.
Correct a comment.

r316625: Do not use -msoft-float with intention of disabling FP on aarch64

r316628: Silence GCC warning by initializing the local variable.

r316654: loader: r316585 did miss userboot update

r316682: loader: r316585 did miss sparc/ofw

r316704: loader.efi: only fetch zfs pool guid for the actual boot device

r316771: loader: Avoid possible overflow via environment variable

r317092: loader: zfs reader vdev_probe should check for minimum device size

r317097: loader: F_READ/F_WRITE should be checked against masked flag

r317099: loader: uboot disk ioctl should call disk_ioctl

r317652: loader.efi: ResetSystem does not use data with EFI_SUCCESS

r317785: zfsboot: drvsize() may be unusable on some systems

r317886: distinguish NFS versus TFTP boot by rootpath

r317887: loader: network read rework

r318142: libstand: NULL pointer dereference in rarp

r318320: loader: add ip layer code into libstand

r318356: libstand: increase nfs max read size to 16k

r318678: Replacing iterating over rootpath by strsep(3).

r318754: Pass -N directly to ld via -Wl rather than passing it to the
compiler driver.

r318982: Pass a "FREEBSD" user-class in PXE dhcp request

r318986: add a comment on vendor index 19 and 20 to avoid confusion

r318987: Support URI scheme for root-path in netbooting

r318988: Always build tftpfs support along with nfs for pxeboot

r318989: Always issue the pxe request

r318990: Partially revert r314948

r318991: Document recent changes on pxeboot

r318992: Capitalize DHCP

r318993: Use the usual FreeBSD spelling for the DHCP user class

r318994: Catch with the change in the user class

r318999: Update the comments concerning net_parse_rootpath to reflect what
it is now

r319083: Followup on the user-class changes

r319084: Small cleanup in dev_net.c

r319085: use the same option list for dhcp discovery and request

r320011: Add chain loader support for loader

r320234: Make structure padding explicit in EFI_MEMORY_DESCRIPTOR

r320288: Allow Clang's integrated assembler to assemble boot0

r320304: loader.efi: Disable smbios for arm

r320467: loader: chain load relocate data declaration is bad

r320482: As with arm64 mark the EFI PE header as allocated on arm.

PR: 218473