C+= (C Plus Equality) is a parody programming language which is allegedly a "feminist" form of C. It was devised in response to this apparently serious (though Poe's Law implies that telling the difference between parody and seriousness in areas of ideological fervor can be difficult) call for a more feminist approach to programming languages. Programs in C+= begin with a "privilege check", and integer variables can hold strings if they feel like it (you're a bigot if you insist they adhere to "traditional" roles).
The creators of this probably hoped to incite another of the series of big flaps in the "War of the Sexes" that have erupted in tech, gaming, atheist/skeptic, and other geeky (and male-dominated) circles, where some incident causes people to take offense and escalate matters, giving commentators a chance to toss in their smartass and dumbass reactions, people and groups with political and social agendas a chance to take sides in another skirmish in the war between Good (i.e., Our Side) and Evil (i.e., the side(s) opposing Our Side), and websites a chance to publish slanted articles with clickbait headlines to pump up page views and ad revenue (and, along the way, labeling the scandal with some silly name ending in -gate). This didn't happen, though; other than a few minor blog mentions, and a series of code repositories kicking the project off, no big fuss happened and the whole thing fizzled out. It doesn't seem to be updated since late 2013.
It appears that program files have a .Xe extension, and header files .Xir.