wmf_free symbol conflict with libwmf

[pbs3141]

Description

The library libwmf already provides a symbol called wmf_free,

/usr/include/libwmf/api.h:

/**
 * free() memory attached to library's memory manager
 */
extern void wmf_free (wmfAPI*,void*);

This conflicts with this library also defining a wmf_free, and prevents them being used in the same process.

Other notes

This bug affects Inkscape (related issue https://gitlab.com/inkscape/inkscape/-/issues/973) which uses both libwmf and libUEMF, and so this symbol had to be renamed uemf_free in the downstream copy.