sql.l: Handle square bracket column names

Credit: @mewalig
Fixes #2

Makefile.am

@@ -17,7 +17,8 @@ EXTRA_DIST = sql.y sql.l \
 	fail3.sql \
 	fail4.sql \
 	ok1.sql \
-	ok2.sql
+	ok2.sql \
+	ok3.sql
 
 sql_SOURCES = exec.c sql-parser.h
 nodist_sql_SOURCES = sql.c sql.tab.c sql.tab.h sql.lex.h

ok3.sql

@@ -0,0 +1 @@
+select [a b] from d;

sql.l

@@ -345,6 +345,7 @@ COUNT    { int c = input(pstate->scanner); unput(c);
 
 [A-Za-z][A-Za-z0-9_]*	{ yylval->strval = strdup(yytext);
                           return NAME; }
+\[(\\.|[^\]\n])*\] |
 `[^`/\\.\n]+`           { yylval->strval = strdup(yytext+1);
                           yylval->strval[yyleng-2] = 0;
                           return NAME; }