added 32-bit linux JNI
Makefile cleanup & preliminary MinGW support

 * care about standard Makefile variables
 * two-phase building: all JNIs bundled in the Jar cannot be built at once so there's
   a separate target "jni" to build one JNI.
   It must be copied into the jni/ directory manually.
 * after all JNIs have been provided, the jar file can be built with the "all" target
added prebuilt windows JNIs

 * these haven't been built with the current source base but should work nevertheless
added sample implementation of a libd2xx_table implementation