MFH: r452019

Merge in updates for mipsn32 and 32-bit arm.

• Brings in upstream commits to fix debugging on mipsn32 (properly parsing registers and signal information in core dumps as well as unwinding across signal frames)
• Brings in upstream commits for reworked ARM support. Compared to the existing patch-armfbsd, this version includes generic FreeBSD target support (auxv, thread names from cores, $_siginfo, syscall names, etc.) as well as VFP support and an unwinder for signal frames.

Approved by: portmgr (swills)