MFC r303555,r303556,r303936,r303962,r304317,r304532,r305026,r305107,r305132,
r305178,r305353,r305814,r306159,r306380,r306504: Loader fixes, 2016q3

r303555: bcache should support reads shorter than sector size

r303556: Improve boot loader quote parsing

r303936: Add kernel environment variables under smbios.system

r303962: Add the missing space between .asciz directive and opening quote
for some lines with #ifdef BTXLDR_VERBOSE/#endif

r304317: boot1.efi Free() should check for NULL to provide consistent
behavior

r304532: Replace sprintf -> snprintf for command_errbuf provisioned from
dynamic content.

r305026: Emulate efi_cons_poll when WaitForKey is not available

r305107: Create a hook 'post-initialize' for people that want to define
something to read in .conf files after all other .conf files for the purpose
of overriding.

r305132: Remove accidentally committed stray comment.

r305178: bd_int13probe() should check extended info if sector info is bad

r305353: Don't use -N to set the OMAGIC with data and text writeable and
data not page aligned.

r305814: ufsread: Do not cast struct direct from void *

r306159: Consistently declare getsecs(void) with proper return type and void
when no arguments are present.

r306380: loader command interpreter should reset command_errmsg

r306504: Fix a cluster of bugs in list EFI environment variables

PR: 204602, 211958, 211958
Relnotes: yes ("Improve boot loader quote parsing")