Fix building against the latest Nix

Dependencies

• [2] FTPCV25M Store aggregate members in the database
• [3] JTHWA6AM Rename aggregate members to constituents
• [*] FV2M6MOT hydra: use autoconf/-make
• [*] 4N5APGRG * Start of a helper tool to evaluate job expressions efficiently.

Change contents

• edit in configure.ac at line 12
  [5.16096]

  [5.16096]
  +

  + CXXFLAGS+=" -std=c++0x"
• replacement in src/c/hydra-eval-jobs.cc at line 159
  [2.473]→[2.473:544](∅→∅)
  − state.coerceToString(*a->value, context, true, false);
  [2.473]

  [2.544]
  + state.coerceToString(*a->pos, *a->value, context, true, false);