Enable picking up mushroom with magic powder in inventory

This is another PW bugfix, but could be useful elsewhere if anybody ever had a reason to allow the player to pick up a mushroom when they already have the magic powder.

Original code:

Code:

$09/8716 AF 44 F3 7E LDA $7EF344[$7E:F344]   A:0D00 X:0000 Y:0007 P:envMXdiZc
$09/871A C9 02       CMP #$02                A:0D00 X:0000 Y:0007 P:envMXdiZc
$09/871C F0 06       BEQ $06    [$8724]      A:0D00 X:0000 Y:0007 P:envMXdiZc
$09/871E A9 01       LDA #$01                A:0D00 X:0000 Y:0007 P:envMXdiZc
$09/8720 87 00       STA [$00]  [$78:0000]   A:0D00 X:0000 Y:0007 P:envMXdiZc
$09/8722 80 2B       BRA $2B    [$874F]      A:0D00 X:0000 Y:0007 P:envMXdiZc
$09/8724 A2 01       LDX #$01                A:0D00 X:0000 Y:0007 P:envMXdiZc
$09/8726 C0 24       CPY #$24                A:0D00 X:0000 Y:0007 P:envMXdiZc
$09/8728 F0 17       BEQ $17    [$8741]      A:0D00 X:0000 Y:0007 P:envMXdiZc


Just NOP out the BEQ $06 at $09871C

Code:

org $09871C
    nop
    nop

Or, if you're the manual hex-editing type:

Code:

0x04871C
F0 06 -> EA EA

Here's another part to add.  This fixes the way the witch in the potion shop handles giving you the magic powder in the following manner:

-You must first give the mushroom to the brewing witch before the magic powder is available (no change, just confirming that this is still the case)
-If you lose the magic powder, a new one will be available at the witches hut, but only so long as the mushroom/powder slot is empty
-If you pick up a second mushroom, you cannot get the powder again until you have gotten rid of the second mushroom
-If you pick up a second mushroom, you cannot give it to the witch to get rid of it if you have the quake medallion (this is PW-specific, so you don't lose the second mushroom).

Code:

seek($04F000)
witch_mushroom_check:
    lda $7EF349
    beq +
    lda #$00
    rtl
+;  lda $7EF344
    rtl


seek($05E462)
    jsl witch_mushroom_check


seek($05F542)
    cmp #$01
    db $10 // beq -> bpl

The witch_mushroom_check subroutine controls the brewing witch outside, whether she will accept the mushroom from you or not. The last section at $05F542 modifies the behavior inside the shop and whether or not the powder is available.