In ansi_c:

In ansi_c:
* Update ansi_c.t for latest pitree, it has default value bug fixed and adds MPFR
* Implement the value field for character constants and string literals
* Add an extra pass for type analysis and constant folding, doesn't support all operators and has just enough implementation to compile the example test.i file
* Implement build() in ansi_c.[ly] to make type analysis and constant folding occur during parsing instead, requires new skeleton code from latest pilex, pitree
* Implement (un)signed_int_value() and float_value() for constructing Value objects directly with a specified precision, instead of cumbersome Value.cast() idea
* Implement mostly complete type analysis and constant folding, compiles nbench

In pilex:
* Make the yy_group_element() routine in the skeleton for pilex --element --groups --python not construct the element until after the text and children are known

In pitree:
* Fix a bug which meant the user had to explictly specify the default value (rather than relying on the built-in null value of each type) if the type was mutable
* Add MPFR type, including default value and serialization/deserialization
* Make the concatenate() routine in the element.py installed by pitree --install-element not construct the element until after the text and children are known