indent: fix indentation of adjacent multi-line initializers

The main topic of this change is parse.c:66, which makes the indentation
of statements uniform with the indentation of other parser symbols.

That change had the side effect of messing up the indentation of files
whose first line does not start in column 1, such as in ps_ind_level.c.
To fix this side effect, the initial indentation must be determined
before pushing the placeholder token psym_stmt during initialization.

branches: 1.7.2;
indent: clean up and condense code

No functional change.

indent: fix indentation of initializers in compound expressions

indent: fix indentation of adjacent '{'

tests/indent: change directive from '#' to '//'

Using a '//' instead of '#' turns the directives into well-formed C
code, resulting in fewer error markers in the editor.

tests/indent: migrate tests for parentheses, brackets, braces

indent: remove FreeBSD IDs

Most of the IDs were empty anyway.

tests/indent: add skeletons for testing tokens and parser symbols

The constants that were previously defined in indent_codes.h were a wild
mixture of tokens from the lexer and symbols on the parser stack. They
were split into separate types starting at indent.h 1.49 from 2021-10-25
and finishing at 1.73 from 2021-10-31.

To match the tests with the new token names, the old tests need to be
migrated to the newly added tests. This will take some time so first
add the skeletons and migrate them in smaller steps, cleaning them up
and extending them on the way.