new metapost, with small mplib/mp.w fixes

source/texk/web2c/mplibdir/ChangeLog

source/texk/web2c/mplibdir/am/libmplib.am

source/texk/web2c/mplibdir/decContext.c

source/texk/web2c/mplibdir/decContext.h

source/texk/web2c/mplibdir/decNumber.c

source/texk/web2c/mplibdir/decNumber.h

source/texk/web2c/mplibdir/decNumberLocal.h

source/texk/web2c/mplibdir/lmplib.c

source/texk/web2c/mplibdir/mp.w

source/texk/web2c/mplibdir/mpmath.w

source/texk/web2c/mplibdir/mpmathdecimal.w

source/texk/web2c/mplibdir/mpmathdouble.w

source/texk/web2c/mplibdir/mpost.w

source/texk/web2c/mplibdir/pngout.w

source/texk/web2c/mplibdir/psout.w

source/texk/web2c/mplibdir/svgout.w