The path-mangling ugliness broke yet again.

The path-mangling ugliness used for previous versions no longer
works. This tweaks it slightly to account for the new VisIt cmake
files.

If the g++ major version number differs from that used to compile
the VisIt binary then the resulting SDF reader will be broken.

There was a bug in one of the cmake files shipped with these
versions of VisIt that was reported here:
https://visitbugs.ornl.gov/issues/1644

This change fixes things up so that the reader plugin can still
be built.

This avoids having to set LD_LIBRARY_PATH in the bash environment to
find sdf_extension.so.
It assumes that the rpath is one level up from the VisIt plugin
directory. This should probably be changed so that it is configurable
from the command line.

build -r wouldn't remove CMake files, which would break attempts to
build after changing VISITPLUGINDIR, for example.

Only major version 1 or 2 of VisIt are supported by the build
script. Anything else should be flagged as an error.
This change also detects if visit has been left in its build
location which does not support the addition of 3rd party plugins.

This fixes SDF/SDF#4 and also fixes EPOCH/epoch#1320

The compiler option '-stdlib=libstdc++' is required for building
on OS-X 10.9
This change adds the flag back again but tests the operating
system to prevent problems on other systems.

It breaks compilation under openSusE 12.2 and Centos 6.5:

  Building CXX object
  CMakeFiles/cmTryCompileExec2143522885.dir/testCXXCompiler.cxx.o

  /usr/bin/c++ -Wno-deprecated -stdlib=libstdc++ -o
  CMakeFiles/cmTryCompileExec2143522885.dir/testCXXCompiler.cxx.o -c
  /home/andrew/CAST_NEW/SDF/VisIt/CMakeFiles/CMakeTmp/testCXXCompiler.cxx

  c++: error: unrecognized command line option ‘-stdlib=libstdc++’

Now it cleans up and rebuilds. Previously it just did a 'make clean'. If
the previous build was 'build -p', this meant that the public copies of
the *.so files would be deleted. Oddly, the users didn't seem to like
that.

To get the previous behaviour, use the option twice: 'build -c -c'.