[libstdc++] Slight doxygen reworking, more markup

[Phil Edwards]

Forgot to mention that the doxygen markup patch also removes trailing
spaces (for some reason that will be sure to entertain psychologists for
years to come, I really hate those *grin*).  Thus the presence of a lot of
apparently no-op lines in the diff.  (Thanks to Stephan for starting this.)

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If ye love wealth greater than liberty, the tranquility of servitude greater
than the animating contest for freedom, go home and leave us in peace.  We seek
not your counsel, nor your arms.  Crouch down and lick the hand that feeds you;
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