Fix `rawTeXParser`. Make macro expansion in raw LaTeX depend on
the setting of the `latex_macros` extension. Previously macros
were always expanded, even in raw TeX in markdown. In addition,
there was previously a bug that caused content to be garbled
in certain cases.
Closes#11253.
Handle `ifstrequal` at a lower level, like the other `if` commands.
See #11253.
