tests: no longer disable -O compiler options

Tests are running without -O since
f377f69fec because some warnings (about
yylval not being initialized) show only when GCC is given -O2.  The
previous patch fixes the warnings. Run the test suite with compiler
options unmodified.

* tests/atlocal.in (O0CFLAGS, O0CXXFLAGS): Remove, use CFLAGS and
CXXFLAGS.

NEWS

@@ -27,6 +27,19 @@ GNU Bison NEWS
 
   will use YY_CALC_LIB_PARSE_H_INCLUDED as guard.
 
+** Fix compiler warnings in the generated parser (yacc.c)
+
+  The compilation of pure parsers (%define api.pure) can trigger GCC
+  warnings such as:
+
+    input.c: In function 'yyparse':
+    input.c:1503:12: warning: 'yylval' may be used uninitialized in this
+                              function [-Wmaybe-uninitialized]
+       *++yyvsp = yylval;
+                ^
+
+  This is now fixed; pragmas to avoid these warnings are no longer needed.
+
 * Noteworthy changes in release 2.6.2 (2012-08-03) [stable]
 
 ** Bug fixes

tests/atlocal.in

@@ -29,16 +29,10 @@ CPPFLAGS="-I$abs_top_builddir/lib @CPPFLAGS@"
 # Is the compiler GCC?
 GCC='@GCC@'
 
-# We want no optimization, as they uncover warnings (therefore,
-# failures) about uninitialized variables in the test suite.  FIXME:
-# fix the warnings, not the flags.
-  O0CFLAGS=`echo '@CFLAGS@'   | sed 's/-O[0-9s] *//g'`
-O0CXXFLAGS=`echo '@CXXFLAGS@' | sed 's/-O[0-9s] *//g'`
-
 # Sometimes a test group needs to ignore gcc warnings, so it locally
 # sets CFLAGS to this.
-  NO_WERROR_CFLAGS="$O0CFLAGS   @WARN_CFLAGS@   @WARN_CFLAGS_TEST@"
-NO_WERROR_CXXFLAGS="$O0CXXFLAGS @WARN_CXXFLAGS@ @WARN_CXXFLAGS_TEST@"
+  NO_WERROR_CFLAGS='@CFLAGS@   @WARN_CFLAGS@   @WARN_CFLAGS_TEST@'
+NO_WERROR_CXXFLAGS='@CXXFLAGS@ @WARN_CXXFLAGS@ @WARN_CXXFLAGS_TEST@'
 
 # But most of the time, we want -Werror.
   CFLAGS="$NO_WERROR_CFLAGS   @WERROR_CFLAGS@"
@@ -51,7 +45,6 @@ BISON_CXX_WORKS='@BISON_CXX_WORKS@'
 if "$at_arg_compile_c_with_cxx"; then
   CC_IS_CXX=1
   CC=$CXX
-  O0CFLAGS=$O0CXXFLAGS
   NO_WERROR_CFLAGS=$NO_WERROR_CXXFLAGS
   CFLAGS=$CXXFLAGS
 else