lint: format tests in a common style

The lint tests do not focus on the whitespace since that is the most
boring part of code style. Therefore, format the tests to be readable
by following share/misc/style as close as possible.

lint: add common header for all tests

For those tests that didn't use GCC-style line markers such as "# 2",
the line numbers of the diagnostics stay the same. This is purely
conincidental. Before, the 3 lines came from lint's built-in
definitions (see 'builtins' in main1.c), and line number counting
continued as if nothing had happened, making the first line of the
actual file line 4. These 3 built-in lines are now replaced with 3
lines of file header.

branches: 1.1.2;
Deprecate tests/util.