Allow enabling -pedantic(-errors) (with -std=c89) for the core.

The core was already -pedantic clean (with default config, with
DEBUGGING almost), cflags just needed some juggling, somewhat
complicated by the logic of -Werror=declaration-after-statement.

Still requires -Dgccansipedantic to enable the -pedantic because
otherwise we do not use things like gcc brace groups and C99 variadic
macros, which are nice.  Also, see below about usedtrace complications.
(the gccansipedantic logic was odd, probably not used for a while.)

Under -DDEBUGGING the -pedantic requires quieting the warnings
about overlong string literals.

Disable -pedantic et al if usedtrace is enabled, it uses too many
non-standard features (and it depends on code generated by an external
framework).