also remove U+007F in header values.

src/headerparser.cc

@@ -41,7 +41,7 @@ std::string robust_to_utf8(sv s)
     
     // NUL bytes confuse C code, especially the Engine.
     // MIME-15: remove all C0 control characters.
-    ret.erase( std::remove_if(ret.begin(), ret.end(), [](char c){ return uint8_t(c) < ' '; } ), ret.end() );
+    ret.erase( std::remove_if(ret.begin(), ret.end(), [](char c){ return uint8_t(c) < ' ' || c=='\177'; } ), ret.end() );
     return ret;
 }