configure: don't automatically disable fastparser with Clang compiler

configure.ac

@@ -127,27 +127,9 @@ AM_CONDITIONAL([HAVE_LIBUTILS], test "$enable_utilities" != "no" -o \
 ######################
 
 AC_ARG_ENABLE([fastparser],
-    AS_HELP_STRING([--disable-fastparser], [Disable use of fastest zone parser]),[],[
-    # Set zone parser type - fastest on release build, slowest on dev build
-    AS_IF([test -d ".git" -o "$PATCH_VERSION" = "dev"],[
-        enable_fastparser=no
-        ],[
-        enable_fastparser=yes
-        ])
-    ])
-
-AX_CC_CLANG
-AS_IF([test "$enable_fastparser" = "yes"],[
-    AS_IF([test -n "$CC_CLANG_VERSION"],[
-      enable_fastparser=no
-      AC_MSG_WARN([Fast zone parser disabled due to possible compiler bug.])
-      AC_MSG_WARN([See https://llvm.org/bugs/show_bug.cgi?id=23490 for details.])
-      AC_MSG_WARN([Use --enable-fastparser=force if your know your clang is fixed.])
-    ])
-])
-
-AS_IF([test "$enable_fastparser" = "force"],[enable_fastparser=yes])
-
+    AS_HELP_STRING([--disable-fastparser], [Disable use of fast zone parser]),
+    [], [AS_IF([test -d ".git"], [enable_fastparser=no], [enable_fastparser=yes])]
+)
 AM_CONDITIONAL([FAST_PARSER], [test "$enable_fastparser" = "yes"])
 
 # GnuTLS crypto backend

m4/ax_cc_clang.m4

-dnl Check to see if the C compiler is clang and which version it is
-dnl
-AC_DEFUN([AX_CC_CLANG],[
-  AC_REQUIRE([AC_PROG_CC])
-  AC_MSG_CHECKING([whether C compiler is clang])
-  CC_CLANG_VERSION=$(
-    $CC -x c -dM -E /dev/null | \
-    $GREP '__clang_version__' | \
-    $GREP -o '".*"' | \
-    $SED 's/^"\(.*\)"$/\1/g'
-  )
-  AC_SUBST([CC_CLANG_VERSION])
-  if test -n "$CC_CLANG_VERSION"; then
-    AC_MSG_RESULT([$CC_CLANG_VERSION])
-  else
-    AC_MSG_RESULT([no])
-  fi
-  ])