C23-compliant parser

[ForNeVeR]

Section 6 Language of the C standard includes a number of EBNF-like definitions Cesium should support.

• [ ] 6 Language
  • [ ] 6.4 Lexical elements: #76
  • [ ] 6.5 Expressions: #207
  • [ ] 6.6 Constant expressions
  • [ ] 6.7 Declarations: #211
  • [ ] 6.8 Statements and blocks: #210
  • [ ] 6.9 External definitions
    • [x] 6.9.1 Function definitions
    • [ ] 6.9.2 External object definitions
  • [ ] 6.10 Preprocessing directives: #77