Ox: Attribute Grammar Compiling System oxml2m4

- new file derived directly from "./libxsd/xsd/cxx/parser/error-handler.hxx", tailored to OXML documents, with all declarations in 'namespace OXML'

- add "Functionality" entry: add support for redirection of the OXML schema location in an OXML macro definition file using an XML catalog
- remove "Known defects & bugs" entry: a more helpful error diagnostic is now issued for a macro parameter reference ('<param id="name" />') within a nested macro definition to a parameter of the enclosing macro definition
- add "Documentation" entry: write an OXML reference manual
- minor wordsmithing

- minor wordsmithing

Tag oxml2m4 release 1.3

- add 'branches' and 'tags' top level directories to the repository

- accidentally omitted from repository:
- used by 'libtool' to portably set library search paths
- lifted from Homebrew gettext v0.26

- update change summary log

- rewrite: Oxml2m4 is now a separately distributed package

- update to Automake & Aclocal version 1.18.1

./oxml2m4/parameter-table.cc
- in 'paramTable::insert ()', if the parameter name to be inserted is a duplicate, throw an 'insert_error' exception
- in 'paramTable::lookup ()', catch an 'std::out_of_range' exception and throw a 'lookup_error' exception