Fix loading libproj in cygwin from OGR

[sam.gillingham@…]

In ogrct.cpp line 150 the code sets the name of the proj shared library to use.
Unfortunately for the cygwin build it tries to load 'libproj.so' which isn't
appropriate since it should be looking for a DLL. I propose the following code
instead:

#ifdef WIN32
#  define LIBNAME      "proj.dll"
#elif defined(__APPLE__)
#  define LIBNAME      "libproj.dylib"
#elif defined(__CYGWIN__)
#  define LIBNAME      "cygproj.dll"
#else
#  define LIBNAME      "libproj.so"
#endif

As you may be aware, cygwin libs get the prefix 'cyg' to show they are linked
against the cygwin dll. ie GDAL comes out as 'cyggdal-1.dll'

Sam.

[Sam Gillingham]

At some stage a cygwin case has been added (maybe at 1.3.x?). Loads libproj.dll instead of cygproj.dll but i'm happy enough with that.