MC: support FK_SecRel_4 for Windows on ARM

Add handling for FK_SecRel_4 (4-byte section relative relocations).  These are
used by the generation of DWARF debug information (the abbrevations use section
relative relocations).  This will also be used in generation of CodeView line
tables.
CodeGen: strengthen WoA AEABI avoidance tests

Add additional test cases for WoA AEABI avoidance checking.
CodeGen: correct memset emittance for WoA

Windows on ARM does not conform to AEABI.  However, memset would be emitted
using the AEABI signature, resulting in inverted parameters.  Handle this
special case appropriately.