fix Agent USA reset vector

src/prelaunch/agent.u.s.a.a

@@ -0,0 +1,29 @@
+;license:MIT
+;(c) 2020 by qkumba
+
+!cpu 6502
+!to "build/PRELAUNCH/AGENT.U.S.A",plain
+*=$106
+
+    !source "src/prelaunch/common.a"
+
+         +ENABLE_ACCEL
+         lda   #$60
+         sta   $36D3
+         jsr   $366D      ; decompress
+
+         ldx   #5
+-        lda   $100,x
+         sta   $300,x
+         dex
+         bpl   -
+         sec
+         rol   $3F3       ; point to $300 instead
+         jsr   $FB6F
+
+         +DISABLE_ACCEL
+         jmp   $837
+
+!if * > $1C0 {
+  !error "code is too large, ends at ", *
+}