Typography fixes: \small, \verb, \mathit and \holtxt are now applied
consistently in DESCRIPTION, Section 1.5.

The rules are:
- \small is applied to \verb and \holtxt but not to math mode ($...$)
- \mathit is applied to all multichar symbols, e.g. "op", "thy", "const"
- there is no space around commas between functions arguments
Typography: "bool" and "num" subscripts are now horizontally aligned.
Typography: missing spaces added.
Consistent use of "failure" instead of "failure occurs".
Do not start a new paragraph in the middle of a sentence.
Missing space added.
Grammar error fixed.