--disable-mathml on Linux to investigate the redness

configure.in

@@ -3118,13 +3118,12 @@ MOZ_ARG_ENABLE_BOOL(ldap-experimental,
     MOZ_LDAP_XPCOM_EXPERIMENTAL=1)
 
 dnl ========================================================
-dnl MATHML on by default
+dnl MATHML
 dnl ========================================================
-MOZ_MATHML=1
-MOZ_ARG_DISABLE_BOOL(mathml,
-[  --disable-mathml      Disable MathML],
-    MOZ_MATHML= )
-AC_SUBST(MOZ_MATHML)
+MOZ_ARG_ENABLE_BOOL(mathml,
+[  --enable-mathml         Enable MathML ],
+    MOZ_MATHML=1
+    AC_DEFINE(MOZ_MATHML))
 
 dnl ========================================================
 dnl SVG