Support PP stringify/merge in #define body expression parsing
pp: Expand macros based on original body tokens instead of AST
Improve "expected" error messages by giving more context information
pp: Fix macro call argument list parsing
pp: Fix #if/#elseif removal
pp: Fix macro expansion
c: Fix dangling AST pointer when ignoring #defines
Add emitting for string/char literals
Fix tkOops() message display
Fix emitting of string/char literals with escape sequences
Fix ppParseIfExprOnly() to work correctly with the latest pp changes
Fix expression parsing (cc5032ca regression)
Improve escape sequence emitting, ensure to not mix with following digits
Fix ppParseIfExprOnly() again
Fix ppParseIfExprOnly() to process #defines/#undefs

so it can figure out the known symbols for #if condition folding.
Update tests
pp: Add support for ## merging involving number literals
ast: Allow merging nested unions/enums too, not just structs