Change 'length modifier' -> 'length field specifier'

It seems unnecessary to use 'modifier', which generally has a very precise meaning in the specification, and isn't the term which seems to be standard when talking about format specifiers.

chapters/operatorsandexpressions.tex

@@ -532,7 +532,7 @@ \subsection{Numeric Functions and Conversion Functions}\label{numeric-functions-
 \end{itemize}
 
 The ANSI-C style \lstinline!format! string (which cannot be combined with any of the other named arguments) consists of a single conversion specifier without the leading \%.
-It shall not contain length modifiers, and shall not use `\lstinline!*!' for width and/or precision.
+It shall not contain a length field specifier, and shall not use `\lstinline!*!' for width and/or precision.
 For all numeric values the type field specifiers `\lstinline!f!', `\lstinline!e!', `\lstinline!E!', `\lstinline!g!', `\lstinline!G!' are allowed.
 For integral values it is also allowed to use the `\lstinline!d!', `\lstinline!i!', `\lstinline!o!', `\lstinline!x!', `\lstinline!X!', `\lstinline!u!', and `\lstinline!c!' type field specifiers (for non-integral values a tool may round, truncate or use a different format if the integer conversion characters are used).