Don't use IF_LINT in Bison sources.

It creates unnecessary differences between the sources that Bison
maintainers build and test (given that maintainers normally
configure with --enable-gcc-warnings) and the sources that Bison
users build.  Instead, use PACIFY_CC, which doesn't.  This change
fixes compiler warnings reported by Tys Lefering at
<http://lists.gnu.org/archive/html/bison-patches/2011-05/msg00004.html>.
* configure.ac: Don't AC_DEFINE lint regardless of the configure
options.  This change affects imported gnulib sources, where
IF_LINT still appears and depends on lint.
* src/scan-gram.l, src/scan-skel.l: Replace uses of IF_LINT with
PACIFY_CC.
* src/system.h (IF_LINT): Remove cpp macro.
(PACIFY_CC): New cpp macro.
(cherry picked from commit 77bb73e7af)

Conflicts:

	src/scan-gram.l

src/scan-gram.l

@@ -138,13 +138,13 @@ splice	 (\\[ \f\t\v]*\n)*
 %{
   /* Nesting level.  Either for nested braces, or nested angle brackets
      (but not mixed).  */
-  int nesting IF_LINT (= 0);
+  int nesting PACIFY_CC (= 0);
 
   /* Parent context state, when applicable.  */
-  int context_state IF_LINT (= 0);
+  int context_state PACIFY_CC (= 0);
 
   /* Location of most recent identifier, when applicable.  */
-  location id_loc IF_LINT (= empty_location);
+  location id_loc PACIFY_CC (= empty_location);
 
   /* Where containing code started, when applicable.  Its initial
      value is relevant only when yylex is invoked in the SC_EPILOGUE
@@ -153,7 +153,7 @@ splice	 (\\[ \f\t\v]*\n)*
 
   /* Where containing comment or string or character literal started,
      when applicable.  */
-  boundary token_start IF_LINT (= scanner_cursor);
+  boundary token_start PACIFY_CC (= scanner_cursor);
 %}