fix to pic-eqn bug fix

[George Sicherman]

[you swing and miss the Bug]

Minor correction:  since the default unit for .sp is v, you need a u
at the end:

	.sp -1-\n(.au

By the way, can anybody suggest a bug fix for the corresponding
problem with superscripts?  You cannot simply override the extra-
space request with \x'0', since troff uses the maximum \x value
over the whole line.
-----
Col. George Sicherman
...seismo!rochester!rocksanne!rocksvax!sunybcs!gloria!colonel
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