Use env variable USERPROFILE instead of HOME for windows and mingw.

re: https://github.com/Unidata/netcdf-c/issues/2380
re: https://github.com/Unidata/netcdf-c/issues/2337

This PARTIALLY fixes some HOME problems because under Windows,
the HOME environment variable may not be set. In that case, use the
USERPROFILE environment variable instead.

libdispatch/ddispatch.c

@@ -81,9 +81,9 @@ NCDISPATCH_initialize(void)
     /* Capture $HOME */
     {
 #if defined(_WIN32) && !defined(__MINGW32__)
-        char* home = getenv("HOME");
-#else
         char* home = getenv("USERPROFILE");
+#else
+        char* home = getenv("HOME");
 #endif
         if(home == NULL) {
 	    /* use cwd */