FreeBSD port of VFS_FSAL

This pull request consists of 15 commits that port VFS_FSAL to FreeBSD platform.


Below is the information needed for getting VFS_FSAL compiled on FreeBSD:

OS : FreeBSD-9  (FreeBSD-8 should be fine too but I don't have build machine to test).
I had krb5 headers/libs and libgssglue installed in /opt/ganesha on my build machine.
Following environment variables were set so that it finds libgssglue :

export CFLAGS="-I/opt/ganesha/include"
export PKG_CONFIG_PATH="/opt/ganesha/lib/pkgconfig/"

Note that commit 564f532 provides preferred path for finding krb5-config which then points to correct version of krb5 headers/libs on build machine.
cmake will say something like this when it probes for KRB5 environment :
-----------
-- found krb5-config here /opt/ganesha/bin/krb5-config
-- Found kerberos 5 headers: /opt/ganesha/include
-- Found kerberos 5 libs: /opt/ganesha/lib/libkrb5.so;/opt/ganesha/lib/libk5crypto.so;/opt/ganesha/lib/libcom_err.so
------------------

This patchset enables only VFS_FSAL so following build command should work :

cmake -DCMAKE_BUILD_TYPE=Maintainer -DBUILD_CONFIG=vfs_pnfs_only