Indent C code in flex and bison files

I suppose we'll do pgindent soon.

I have semi-manually gone through the various .l and .y files and fixed 
up the formatting of the C code to be more in line with pgindent style. 
Most of that code was old, so I don't expect this to be such a large 
effort going forward.  I also think a lot of that code started as 
copy-and-paste, so having "correct" style will also help future code use 
better style by default.

The patch is rather large, so I won't post it here, but you can see it here:

https://github.com/petere/postgresql/compare/master...petere:indent-gram-scan.patch

I propose to apply this after the main pgindent run is done.