Get rid of trailing semicolons in C macro definitions.

Writing a trailing semicolon in a macro is almost never the right thing,
because you almost always want to write a semicolon after each macro
call instead.  (Even if there was some reason to prefer not to, pgindent
would probably make a hash of code formatted that way; so within PG the
rule should basically be "don't do it".)  Thus, if we have a semi inside
the macro, the compiler sees "something;;".  Much of the time the extra
empty statement is harmless, but it could lead to mysterious syntax
errors at call sites.  In perhaps an overabundance of neatnik-ism, let's
run around and get rid of the excess semicolons whereever possible.

The only thing worse than a mysterious syntax error is a mysterious
syntax error that only happens in the back branches; therefore,
backpatch these changes where relevant, which is most of them because
most of these mistakes are old.  (The lack of reported problems shows
that this is largely a hypothetical issue, but still, it could bite
us in some future patch.)

John Naylor and Tom Lane

Discussion: https://postgr.es/m/CACPNZCs0qWTqJ2QUSGJ07B7uvAvzMb-KbG2q+oo+J3tsWN5cqw@mail.gmail.com

contrib/pg_trgm/trgm.h

@@ -44,7 +44,7 @@ typedef char trgm[3];
 	*(((char*)(a))+0) = *(((char*)(b))+0);	\
 	*(((char*)(a))+1) = *(((char*)(b))+1);	\
 	*(((char*)(a))+2) = *(((char*)(b))+2);	\
-} while(0);
+} while(0)
 
 #ifdef KEEPONLYALNUM
 #define ISWORDCHR(c)	(t_isalpha(c) || t_isdigit(c))