Older versions of GCC, the HP compiler, and the SGI MIPSpro compiler do
not like the use of make_pair in this case and the conversions it
requires:

  a value of type "const char *" cannot be used to initialize an entity
  of type "char [1]"

  /usr/include/g++-3/stl_pair.h:68: assignment of read-only location

Instead use a map lookup pattern already used throughout the rest of our
source tree.