INT 2F - CS_TSR specification - GET HANDLE (TSR-SPECIFIC INSTALLATION CHECK)

	AX = 8001h
	DS:SI -> ASCIZ signature string for desired TSR (see #02929)
Return: BX = process handle or 0000h if specified TSR not installed
	ES:DI -> process block for TSR (see #02928) if BX<>0000h
Note:	A widely-available copy of ASCII billing itself as "ASCII 2.OO by
	  Nick Zaikin Jr." is in fact a hacked copy of the Compact Soft
	  ASCII v4.23 which is identical except for the changed attribution
	  and version (in fact, some instances of "4.23" were missed); the
	  hacked copy requires the signature string
	  "ASCII 2.OO by Nick Zaikin Jr." instead of the unhacked version's
	  simple signature "ASCII"
SeeAlso: AX=8000h"CS_TSR",AX=8002h"CS_TSR"