[wip/genom3] Update to 2.99.15

Changes since 2.99.14:

 . Added 'native' IDL keyword. The meaning is slightly different from that of
   the OMG IDL. GenoM 'native' keyowrd defines a new opaque type, that can be
   used only in codels (or IDS). The type is manipulated as a pointer by GenoM
   and the templates, and codels are responsible for the actual type
   definition or memory management. This is typically used to store types in
   the IDS that cannot be represented as IDL (external types, opaque types,
   etc.).

 . Renamed #pragma native to #pragma masquerade. This is to avoid confusion
   with the new 'native' IDL keyword. The #pragma purpose is also hopefully
   clearer.

 . Updated mappings for the IDL 'char' type. 'char's are now mapped to
   uint8_t in C/C++, so that the C 'char' type is reserved for strings.

 . Fixed grammar to allow compound initializers with just a doc string and no
   value.

 . Improved syntax error handling in the parser. In particular, missing
   semicolons or syntax erros in codels parameters should not spew loads of
   errors anymore.

 . Updated skeleton template to generate $component-genom.pc instead of
   lib$component_codels.pc, because the top level package is most often used in
   other genom components to include a part of the interface (rather than
   linking with the codels).

 . Fixed skeleton '-l c++' option for compiling codels with a C++ compiler.

 . Temporary disabled support for C++ codels interface. This will not be
   supported in 3.0, but remains on the TODO list. C++ codels must use the C
   interface in the meantime.

 . Fixed a bunch of minor bugs and added respective regression tests.