patch for bugs 1447850 and 1447382

Patch for libuemf. ----- Somewhere along the line during the clang patches the version of libUEMF in inkscape acquired changes not in the upstream library. Small patch which puts them back in sync.

Patch for several issues in libuemf. ----- The patch: 1. Removes half a dozen or so code lines that didn't do anything. 2. Fixes a couple of missing tests for pointers which cannot be NULL. (Note that in many instances the pseudoobject functions in upmf.c do accept null pointers because the objects being constructed have optional parts.) 3. There was one "real" potential memory leak (line 6276 in upmf.c, numbers before the patch). I fixed the others too, but they just never happen (iconv would have to fail in some strange way.) There are no (real) memory access violations or memory leaks in any of this either in standalone libUEMF testing or in use as part of Inkscape as determined from valgrind runs.

fix self-assignment. use of UNUSED macro to better show the intent of the code

libUEMF update; EMF linear gradient bug fixes (bug #1263242)

Move libuemf to a separate directory. Rename libunicode-convert to symbol_convert and put it in libuemf.