util: Add function FormatParagraph to format paragraph to fixed-width

This is to be used for the `-version` and `-help` messages.

src/util.h

@@ -286,6 +286,11 @@ inline std::string HexStr(const T& vch, bool fSpaces=false)
     return HexStr(vch.begin(), vch.end(), fSpaces);
 }
 
+/** Format a paragraph of text to a fixed width, adding spaces for
+ * indentation to any added line.
+ */
+std::string FormatParagraph(const std::string in, size_t width=79, size_t indent=0);
+
 inline int64_t GetPerformanceCounter()
 {
     int64_t nCounter = 0;