silence a `bcheck' warning `read from uninitialized memory' (bison yylval)

ChangeLog

@@ -1,3 +1,9 @@
+2011-02-11  Robert Larice
+ * src/frontend/parse-bison.y :
+    silence a `bcheck' warning `read from uninitialized memory'
+      yylval in the bison generated parser is copied,
+      even when the value is actually unused
+
 2011-02-11  Robert Larice
  * src/spicelib/devices/vsrc/vsrcask.c :
     add a missing `ask' function for VSRC_TRRANDOM

src/frontend/parse-bison.y

@@ -98,6 +98,11 @@
 %left   '[' ']'
 %left   TOK_LRANGE TOK_RRANGE
 
+%initial-action      /* initialize yylval */
+{
+    $$.num = 0.0;
+};
+
 %%
 
 /*