INT 62 u - FGDRIVER v4.02 - "FG_MOUSEBUT" - GET MOUSE BUTTON PRESS/RELEASE CNTS
	AX = 0074h
	CX = mouse button (1 = left press, 2 = right press, 3 = middle press,
		  -1=left release, -2=right release, -3=middle release)
	ES:BX -> variable pointer record (see #03490)
Return: variables updated
Notes:	the FGDRIVER functions are rearranged with each major release, but
	  their parameters do not change (see #03474 at AX=0000h)
	This function returns the count of presses or releases since the last
	  call to this function; if the count is zero, row and column will
	  also be zero
SeeAlso: AX=0075h,AX=0077h,AX=007Ah


Format of FGDRIVER MOUSEBUT variable pointer record:
Offset	Size	Description	(Table 03490)
 00h	WORD	segment of WORD buffer for press/release count
 02h	WORD	offset of WORD buffer for press/release count
 04h	WORD	segment of WORD buffer for screen space col of last press/rls
 06h	WORD	offset of WORD buffer for screen space col of last press/rels
 08h	WORD	segment of WORD buffer for screen space row of last press/rls
 0Ah	WORD	offset of WORD buffer for screen space row of last press/rls