Improved MANPATH handling
Fixed swmod operation return code handling
Improved PKG_CONFIG_PATH handling
Added swmod command hostspec and additional online help about HOSTSPEC.
Added output of new install prefix to "swmod setinst"
Added automatic generation of "configure file to "swmod configure"

Also changed "swmod install" accordingly and improved online help.
Added "swmod instpkg"
Removed "make clean" and similar before and after from "swmod install"

For a clean installation, now use "swmod instpkg ." instead.
Removed explicit support for CERN ROOT System ROOTSYS variable

The ROOT-System itself does not use the ROOTSYS variable anymore since
version 5.20. Most software that links against ROOT is able to detect
the root installation using the "root-config" tool now. If the ROOTSYS
variable is still necessary in some special cases, it can be set now using
an swmodrc.sh script.
Added support for special dependency "!clflags" to "swmod load"
Added swmod functions swmod_is_valid_prefix and swmod_version_match
Bugfix in swmod_getprefix
Changed swmod to skip loading of already modules

If the most recently loaded version of a module is the same as the
currently requested version, the module is not loaded again.
Added auto-clean to "swmod install"