Emit a warning diagnostic if a symbol was promoted
to a variable.  This helps people figure out what
happened if they tried to do something to the variable
and it didn't work because we gave it the default type
of void*.
Fix two pedantic issues with our builtin headers. The __STDC_VERSION__
for C99 is '199901L' and we shouldn't be comparing it with anything
else.

Neither of these should have had any impact in practice.