* New feature check macro system. See _PDCLIB_aux.h for details

 * remove "#pragma weak" from strdup.c. It's nonportable and shouldn't be
   necessary
 * <string.h> changed to use new feature test system for strdup + strndup
 * add strndup implementation
 * <assert.h> more reliable handling of error messages

 Build system:
 * The CoreMake system is dead. It proved to be unscalable
 * The old Make based system is gone, also
 * We now use a Jam based system (requires the latest FT_Jam). Reasons:
  * Make is hard to scale in a non-recursive manner. The interactions get
    intractably complex
  * The build system depended upon GNU Make. GNU Make's license (the GPLv3) is
    about as diametrically opposed to PDCLib's CC0 as you can get without being
    closed source
  * Jam is actually more portable. In particular, it doesn't require a Unix
    emulation layer (unlike GMake)
  * The Jam system, as is, can be incorporated into the build system of a larger
    project.

Why Jam?
 * GNU make is too low level. It also incorporates too much magic: it can spend
   significant ammounts of time trying to update source files from SCCS and RCS
   files for example (a feature it is doubtful somebody has used in the last
   decade)
 * Systems like CMake are too high level: CMake is very difficult to use in a
   cross compilation environment.
 * Systems like Scons and Waf pose similar issues. Scons is also incredibly
   slow.