QTextDocument::FindWholeWords does not work as expected

QTextDocument::find() and other find functions do not correctly handle words with underscores.

Example: Qt Assistant, qmake Variable Reference - on this page there are multiple words with underscores such as QMAKE_CC and QMAKE_CFLAGS_DEBUG. If ones searches for QMAKE in "Whole words" mode, one is not interested in those word combinations with underscores but the find functions hit them all. That is not the standard behavior. See find feature in Eclipse, for example.