Remove mingw plus some compilers no longer being tested from required list

[SVN r41330]

status/explicit-failures-markup.xml

@@ -25,15 +25,10 @@
     <!-- /////////////// Toolsets /////////////// -->
     <mark-toolset name="acc" status="required"/>
     <mark-toolset name="darwin-4.0.1" status="required"/>
-    <mark-toolset name="gcc-3.4.3_sunos" status="required"/>
-    <mark-toolset name="gcc-3_4_4_tru64" status="required"/>
     <mark-toolset name="gcc-4.1.2_sunos_i86pc" status="required"/>
     <mark-toolset name="gcc-4.1.3_linux" status="required"/>
     <mark-toolset name="gcc-4.2.1" status="required"/>
     <mark-toolset name="gcc-4.2.1_linux_x86_64" status="required"/>
-    <mark-toolset name="gcc-4_0_3_tru64" status="required"/>
-    <mark-toolset name="gcc-cygwin-3.4.4" status="required"/>
-    <mark-toolset name="gcc-mingw-3.4.5" status="required"/>
     <mark-toolset name="hp_cxx-71_006_tru64" status="required"/>
     <mark-toolset name="intel-linux-9.0" status="required"/>
     <mark-toolset name="intel-vc8-win-10.0" status="required"/>