[bitmask.types] Reword bitmask types

Author: frederick-vs-ja

source/lib-intro.tex

@@ -641,7 +641,7 @@
 \rSec4[bitmask.types]{Bitmask types}
 
 \pnum
-Several types defined in \ref{\firstlibchapter} through \ref{\lastlibchapter}
+Several types specified in \ref{\firstlibchapter} through \ref{\lastlibchapter}
 and \ref{depr} are
 \defnx{bitmask types}{type!bitmask}.
 Each bitmask type can be implemented as an