Revert "Fix bogus %name-prefix option syntax in all our Bison files."

This reverts commit a670f5ed1a.

It turns out that the %name-prefix syntax without "=" does not work
at all in pre-2.4 Bison.  We are not prepared to make such a large
jump in minimum required Bison version just to suppress a warning
message in a version hardly any developers are using yet.
When 3.0 gets more popular, we'll figure out a way to deal with this.
In the meantime, BISONFLAGS=-Wno-deprecated is recommendable for
anyone using 3.0 who doesn't want to see the warning.

contrib/cube/cubeparse.y

@@ -39,7 +39,7 @@ static NDBOX * write_point_as_box(char *s, int dim);
 /* BISON Declarations */
 %parse-param {NDBOX **result}
 %expect 0
-%name-prefix "cube_yy"
+%name-prefix="cube_yy"
 
 %token CUBEFLOAT O_PAREN C_PAREN O_BRACKET C_BRACKET COMMA
 %start box

contrib/seg/segparse.y

@@ -42,7 +42,7 @@
 /* BISON Declarations */
 %parse-param {SEG *result}
 %expect 0
-%name-prefix "seg_yy"
+%name-prefix="seg_yy"
 
 %union {
   struct BND {

src/backend/bootstrap/bootparse.y

@@ -93,7 +93,7 @@ static int num_columns_read = 0;
 %}
 
 %expect 0
-%name-prefix "boot_yy"
+%name-prefix="boot_yy"
 
 %union
 {

src/backend/parser/gram.y

@@ -134,7 +134,7 @@ static TypeName *TableFuncTypeName(List *columns);
 
 %pure-parser
 %expect 0
-%name-prefix "base_yy"
+%name-prefix="base_yy"
 %locations
 
 %parse-param {core_yyscan_t yyscanner}

src/interfaces/ecpg/preproc/ecpg.header

@@ -464,7 +464,7 @@ add_typedef(char *name, char * dimension, char * length, enum ECPGttype type_enu
 %}
 
 %expect 0
-%name-prefix "base_yy"
+%name-prefix="base_yy"
 %locations
 
 %union {

src/pl/plpgsql/src/gram.y

@@ -108,7 +108,7 @@ static	List			*read_raise_options(void);
 %}
 
 %expect 0
-%name-prefix "plpgsql_yy"
+%name-prefix="plpgsql_yy"
 %locations
 
 %union {