[stdfloat.syn] Use "declare" for typedef-names

Author: frederick-vs-ja

source/support.tex

@@ -1993,7 +1993,7 @@
 \rSec2[stdfloat.syn]{Header \tcode{<stdfloat>} synopsis}
 
 \pnum
-The header \libheader{stdfloat} defines type aliases for
+The header \libheader{stdfloat} declares type aliases for
 the optional extended floating-point types that are specified in
 \ref{basic.extended.fp}.