pg_bsd_indent - improvements around offsetof and sizeof

Hello,

I think I've managed to improve pg_bsd_indent's handling of two types of 
cases.

The first are like in this example:
-	hashp = (HTAB *) DynaHashAlloc(sizeof(HTAB) + strlen(tabname) +1);
+	hashp = (HTAB *) DynaHashAlloc(sizeof(HTAB) + strlen(tabname) + 1);
Pristine pg_bsd_indent is inconsistent in masking parentheses as those 
that are part of a cast and those that "are part of sizeof": seeing a 
type name following an lparen it always masks that lparen as a part of a 
cast; seeing an rparen it only removes the bit if it doesn't overlap 
with sizeof_mask. In the example above, "(HTAB" started both "cast 
parens" and "sizeof parens" at the same time, and the immediately 
following rparen ended only the "sizeof parens". According to indent, 
the cast-to type then ends at "tabname)" and what follows is the cast's 
operand, including the + operator; in that case it's assumed to be unary 
and not binary, which is why indent doesn't add the space after it.
The fix was to make it consistent about masking parens:
-					ps.cast_mask |= 1 << ps.p_l_follow;
+					ps.cast_mask |= (1 << ps.p_l_follow & ~ps.sizeof_mask);

The second type of cases are like this:
-	nse = palloc(offsetof(PLpgSQL_nsitem, name) +strlen(name) + 1);
+	nse = palloc(offsetof(PLpgSQL_nsitem, name) + strlen(name) + 1);
pg_bsd_indent simply hasn't been taught that a parenthesized type name 
following the offsetof macro and then an lparen is another exception to 
the rule of thumb that a construction like that generally means a cast.

You'll also notice other, seemingly unrelated changes, most notably the 
rearrangement in numbers assigned to keywords. I've done it that way so 
that it was easier and simpler to keep the -bs option functioning as 
designed.

I've also renamed "sizeof_mask" to "not_cast_mask", because I think the 
latter is a better description of what the mask does (it prevents 
interpreting parenthesized type names as a cast where they aren't, 
namely where they follow sizeof or offsetof; I haven't done any support 
for function declarators and I don't plan to - the fact that 
pg_bsd_indent thinks that "(int" in "char func(int);" begins a cast is 
amusing but it seems harmless for now).

I'm attaching the patch for pg_bsd_indent and also a full diff that 
shows the change in its behavior when run against PG's sources.