Doc: Corrected doc string for ly:dimension? (issue 547470049 by address@hidden)

[davidgrant . no]

Reviewers: ,

Message:
It isn't clear to me how a dimension is different from a normal number,
but the current doc string seems to be incorrect all the same.

Description:
Doc: Corrected doc string for ly:dimension?

ly:dimension? is a predicate - it does not return a number.

Please review this at https://codereview.appspot.com/547470049/

Affected files (+1, -1 lines):
  M lily/general-scheme.cc


Index: lily/general-scheme.cc
diff --git a/lily/general-scheme.cc b/lily/general-scheme.cc
index 
629c85ccaa7483d542d16d54e548279d2a401483..3cad1775d2754768aa3b39f7608f5b83f0d4316e
 100644
--- a/lily/general-scheme.cc
+++ b/lily/general-scheme.cc
@@ -260,7 +260,7 @@ LY_DEFINE (ly_unit, "ly:unit", 0, 0, 0, (),
 }
 
 LY_DEFINE (ly_dimension_p, "ly:dimension?", 1, 0, 0, (SCM d),
-           "Return @var{d} as a number.  Used to distinguish length"
+           "Is @var{d} a dimension?  Used to distinguish length"
            " variables from normal numbers.")
 {
   return scm_number_p (d);