[character.seq] Use \tcode and \placeholder to style placeholders

Author: tkoeppe

source/lib-intro.tex

@@ -759,10 +759,10 @@
 \item
 A
 \term{character sequence}
-is an array object~(\ref{dcl.array}) \textit{A} that
+is an array object~(\ref{dcl.array}) \tcode{\placeholdernc{A}} that
 can be declared as
-\tcode{\textit{T A}[\textit{N}]},
-where \textit{T} is any of the types
+\tcode{\placeholdernc{T\;A}[\placeholder{N}]},
+where \tcode{\placeholder{T}} is any of the types
 \tcode{char},
 \tcode{unsigned char},
 or
@@ -774,7 +774,7 @@
 array have defined contents up to and including an element determined by some
 predicate.
 A character sequence can be designated by a pointer value
-\textit{S} that points to its first element.
+\tcode{\placeholder{S}} that points to its first element.
 \end{itemize}
 
 \rSec5[byte.strings]{Byte strings}