zmat fails to build with octave 7.1

[opoplawski]

When trying to build the Fedora octave-zmat file with octave 7.1, make oct fails with:

CXXFLAGS='-O3' LFLAGS='' LDFLAGS='' mkoctfile zmat.cpp  -o ../zipmat zmatlib.o lz4/lz4.o lz4/lz4hc.o easylzma/compress.o easylzma/decompress.o easylzma/lzma_header.o easylzma/lzip_header.o easylzma/common_internal.o easylzma/pavlov/LzmaEnc.o easylzma/pavlov/LzmaDec.o easylzma/pavlov/LzmaLib.o easylzma/pavlov/LzFind.o easylzma/pavlov/Bra.o easylzma/pavlov/BraIA64.o easylzma/pavlov/Alloc.o easylzma/pavlov/7zCrc.o --mex -I../include -Ieasylzma -Ieasylzma/pavlov -Ilz4 
make: *** [Makefile:148: ../zipmat] Error 127

This is because it appears that mkoctfile-7.1.0 calls $CXX and with CXX=mkoctfile it create and infinite recursive loop. There may be something special about the Fedora rpm build environment that causes the CXX variable to get exported as I can run 'make oct' by hand without any trouble. But I think the zmat makefile needs to handle calling mkoctfile in a different way.