allow long_name to be used without specifying a latex name, #478

(cherry picked from commit 54b3a18ceda3091593dbcb84184050ef32dc3782)
write_latex_definitions: use longtable, #478

(cherry picked from commit 3539dc71535c0fee6259f2f9900f002f2d2817aa)
write_latex_definitions: use texttt for variable names, #478

(cherry picked from commit 10652be09a874d39fa551b65f7745f7e522dd72d)
write_latex_definitions: remove lines that prevented this code from being included in a larger latex doc
(cherry picked from commit 2d966208c4b128a64be9503f4c275f5410964473)