add more explanations of byte sequences

strings/488A489848

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+Preserve registers on stack
+
+This is the standard form of saving the A X and Y registers on the stack
+
+PHA
+TXA
+PHA
+TYA
+PHA
+
+See, for example: 
+
+http://6502.org/tutorials/register_preservation.html
+
+Not copyrightable.

strings/68A868AA

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+PLA / TAY / PLA / TAX sequence
+
+This is a common sequence for restoring registers from the stack.
+It is a fragment of the reverse of pushing the registers A X and Y
+in alphabetic order. Not copyrightable.

strings/68A868AA6840

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+End of interrupt restore registers and resume sequence
+
+This is the standard form of returning from an interrupt on a 6502:
+
+PLA
+TAY
+PLA
+TAX
+PLA
+RTI
+
+See, for example: 
+
+http://6502.org/tutorials/register_preservation.html
+
+Not copyrightable.

strings/820260

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+tail end of access to $0282, followed by RTS
+
+This small fragment is a return from subroutine, where
+the last thing the subroutine does is access memory location $0282.
+This is not copyrightable.

strings/840260

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+tail end of access to $0284, followed by RTS
+
+This small fragment is a return from subroutine, where
+the last thing the subroutine does is access memory location $0284.
+This is not copyrightable.

strings/8A489848

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+Preserve registers on stack
+
+This is the standard form of saving the A X and Y registers on the stack
+
+PHA
+TXA
+PHA
+TYA
+PHA
+
+See, for example: 
+
+http://6502.org/tutorials/register_preservation.html
+
+Not copyrightable.

strings/A868AA6840

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+End of interrupt restore registers and resume sequence
+
+This is the standard form of returning from an interrupt on a 6502:
+
+PLA
+TAY
+PLA
+TAX
+PLA
+RTI
+
+See, for example: 
+
+http://6502.org/tutorials/register_preservation.html
+
+Not copyrightable.

strings/B00320

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+Branch over following JSR instruction
+A branch with argument $03 skips the following 3 bytes.
+A JSR instruction has the initial byte value of $20.
+Therefore $F0 $XX $20 is part of a 
+Bxx +
+JSR $xxxx
+*
+
+instruction sequence.
+This is a very common construction, and the logical way to 
+conditionally call a routines, and therefore is not copyrightable.

strings/B0034C

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+Jump conditionally
+
+Conditionally take a JMP
+
+Bxx +
+JMP $xxxx
+*
+
+This is a very common instruction sequence.
+Not copyrightable.

strings/F0034C

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+Jump conditionally
+
+Conditionally take a JMP
+
+Bxx +
+JMP $xxxx
+*
+
+This is a very common instruction sequence.
+Not copyrightable.