- Makefile, kernel/posix_compatibility.h/.cc: provide POSIX.2008 fake implementation...

 - Makefile, kernel/posix_compatibility.h/.cc: provide POSIX.2008 fake implementation of open_memstream()/fmemopen() for pre-POSIX.2008 systems.
 - Makefile: OSX build rules (Apple's gcc and clang have no -rdynamic option and no librt).
 - Makefile: Generate debugger symbols and don't optimize for size in debug target (otherwise the debugger pretty hard to use).
 - Makefile: Reorder target concatenation in order to avoid use-before-built problems for source-include and linker dependencies.
 - Makefile: On OSX/macports, qmake-qt4 is named 'qmake' (the default Qt4 installation name, unless the distribution changes it).
 - Makefile: For OSX/Macports, we need to pass -I/opt/local/include and -L/opt/local/lib to give GNU libraries precedence over Apple's.
 - Makefile: Build a local minisat copy just like abc (to avoid dependency on broken/unmaintained distribution header files).
 - .gitignore: Ignore minisat directory.