Bug#893188: mapnik: add mips* back to arch list

[YunQiang Su]

Package: src:mapnik
Version: 3.0.19+ds-1

With some test on mips64el/mipsel machines, mapnik builds well,
without memory exhibition problems.

I think it should be fixed now,  with
  1) We update some hardware of mips*, dropped some old Loongson 2E machines.
  2) Set -param ggc-min-expand default now on mips/mipsel.

It should be OK to add these architectures back.

The full mips* arch list:
   mips mipsel mipsn32 mipsn32el mips64 mips64el
   mipsr6 mipsr6el mipsn32r6 mipsn32r6el mips64r6 mips64r6el

If you feel OK, I suggest we can use any now,

At least please add
   mips mipsel mips64el mips64r6el

-- 
YunQiang Su