Launcher (MacOSX >= 10.7): re-execute when DYLD_LIBRARY_PATH needs to be set

As reported by Ilan Tal, MacOSX no longer respects user-set
DYLD_LIBRARY_PATH (unless the environment variable is set before
launching the program):

	http://support.apple.com/kb/TS4267

So starting from MacOSX version 10.7, we now re-execute the launcher
with the correct DYLD_LIBRARY_PATH.

Note: the Java property java.library.path helps only partially here:
.dylib files in that directory are found correctly, but if those
libraries want to find other files in the same directory, they fail.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>