MinGW: Define DEFAULTPATH as needed
MinGW: Define DEFAULTPATH as needed

Currently, "make install" installs the data directory in
share/link-grammar, but the DEFAULTPATH definition assumes that _WIN32
only means MSVC, for which we don't have an installation script (yet).
So invoking link-parser from a user directory, without argument or with
a 2-letter language as argument, doesn't find a dictionary.

linas/link-grammar,ampli/link-grammar,ampli/link-grammar,linas/link-grammar,linas/link-grammar,opencog/link-grammar,linas/link-grammar,ampli/link-grammar,linas/link-grammar,opencog/link-grammar,opencog/link-grammar,opencog/link-grammar,linas/link-grammar,ampli/link-grammar,ampli/link-grammar,opencog/link-grammar,ampli/link-grammar,opencog/link-grammar,opencog/link-grammar,ampli/link-grammar,ampli/link-grammar,linas/link-grammar,opencog/link-grammar,opencog/link-grammar,linas/link-grammar,linas/link-grammar,ampli/link-grammar