mparse_alloc
mp = mparse_alloc(MPARSE_SO | MPARSE_UTF8 | MPARSE_LATIN1 |
mp = mparse_alloc(options, os_e, os_s);
struct mparse *mparse_alloc(int, enum mandoc_os, const char *);
mp = mparse_alloc(mparse_options, MANDOC_OS_OTHER, NULL);