replace_tag: Updates and adds doxygen options in a line string vector
In rdoxygen: Create Doxygen Documentation for Source Code

Scans the lines and changes the value for the named tag if one line has this tag, adds a line at the end if no line has this tag and returns a warning if several lines match the tag.

1	replace_tag(fileStrings, tag, newVal)

`fileStrings`	A vector with each string containing a line of the file
`tag`	A string with the tag to be searched for
`newVal`	A string with the new value for the tag