Add support for "R" models

"U" models are explicitly supported, and it's not made clear that "R" models are equally supported.
Adding support for "W" models
Added "W" & "R" support from README.txt to .md
termcap: add gitignore
gdb: updated gitignore
Bumped revision to 376.47 alpha1
Merge with GPL 376_2678 (from RT-AC87 release)
snmp: Fix building on QTN platform
snmp: Remove missing mib
snmp: Cleaned up build environment
snmpd: Added option to build profiles, disabled by default
webui: report Quantenna FW version on the Sysinfo page
bwdpi: add library that got filtered out of the 2678 GPL merge
aicloud: merge MIPS prebuild binaries from RT-N16 376_2678 release
aicloud: merge non-QTN ARM prebuild binaries from RT-N18 376_2678 release
Updated prebuild binary blobs for pw encoding/decoding
Updated documentation
snmpd: Add option to control WAN access, and leave it disabled by default
libiconv: added gitignore
snmpd: Added missing pre-requisites to build, fixing building from a clean repo