MFC r257037: Redefine the io provider using the SDT(9) macros

MFC slacker:	markj
MFC r250817: Use SDT_PROBE1() instead of SDT_PROBE()

MFC slacker:	pjd
MFC r251237: Port the SDT test
MFC r227294: SDT's struct sdt_argtype can be marked static everywhere

MFC slacker:	ed