Suppress wxKeyNames missing field initializers warnings again

This reapplies 15d9067006 which was
reverted in daae25753e for some reason,
but is still needed as we get a bunch of -Wmissing-field-initializers
from gcc 8 without it.

See https://github.com/wxWidgets/wxWidgets/pull/1463

src/common/accelcmn.cpp

@@ -38,6 +38,8 @@ wxAcceleratorTable wxNullAcceleratorTable;
 // wxAcceleratorEntry implementation
 // ============================================================================
 
+wxGCC_WARNING_SUPPRESS(missing-field-initializers)
+
 static const struct wxKeyName
 {
     wxKeyCode code;
@@ -113,6 +115,7 @@ static const struct wxKeyName
     { WXK_COMMAND,          /*TRANSLATORS: Name of keyboard key*/ wxTRANSLATE("Command") },
 };
 
+wxGCC_WARNING_RESTORE(missing-field-initializers)
 
 // return true if the 2 strings refer to the same accel
 //