
The macro tt(UNDEFINEMACRO) removes a definition of a macro that was defined
by tt(DEFINEMACRO). This macro takes one argument: the macro name to remove.

There is no error condition (except for syntax errors): when no macro with a
matching name was previously defined, no action is taken.

For example, the safe way to define a macro is by first undefining it. This
ensures that possible previous definitions are removed first:

verb(\
UNDEFINEMACRO(mymacro)
DEFINEMACRO(mymacro)(1)(This is my macro with argument ARG1.))
