Always include MuPDF's version of memento.h
Always include MuPDF's version of memento.h

Previously for memento builds MuPDF would include on memento.h from
the include directory, but for any other type of build MuPDF would
get memento.h from thirdparty/jbig2dec. This is wrong especially
if the two memento implementations exhibit verison skew.

Since MuPDF always builds memento.c we must always set
MEMENTO_MUPDF_HACKS so that the memento.h from include/mupdf is used.
This commit fixes that.

ArtifexSoftware/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,ccxvii/mupdf,ccxvii/mupdf,ccxvii/mupdf,ccxvii/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf,ccxvii/mupdf,ArtifexSoftware/mupdf,ArtifexSoftware/mupdf,ccxvii/mupdf,ArtifexSoftware/mupdf,TamirEvan/mupdf,ArtifexSoftware/mupdf