MPI-Bash v1.2

This release represents a few improvements to the build process. First, a --with-plugindir option lets a user easily override the directory in which mpibash.so and circlebash.so get installed. Second, the mpibash wrapper script is cleaner and more robust. Third, scripts that rely on Circle-Bash are not installed if Circle-Bash is not installed (typically because Libcircle was not available at configuration time).

There are no changes to the implementation of any of the MPI-Bash (or Circle-Bash) loadable builtin functions. However, the mpibash wrapper script no longer defines the MPIBASH_PLUGIN and CIRCLEBASH_PLUGIN environment variables. Instead, it puts the plugins in the LD_LIBRARY_PATH so a simple enable -f mpibash.so mpi_init will work.