gEDA-dev: pcb: Add a concatenated expressions example to the manual

[Kai-Martin Knaak]

Please add to the manual an example how to concatenate individual 
expressions. 

Proposal:

Individual regular expressions can be concatenated with the "|" 
character. The resulting string will match all elements that match any of 
the individual expressions.  The string "R1|R3|R9" will match the 
resistors R1, R3 and R9

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Kai-Martin Knaak
http://lilalaser.de/blog