The global "tags" can be iterated upon for every unique tag which is set in the
level. If a tag is set on a sector/line/thing, it will be included. Taking the
length of "tags" will give you the number of these unique tags. (If a tag is
set on multiple sectors/lines/things, it will only be counted once though.)

For sectors, lines and mapthings, call the field "tagged". This function takes
one argument, which is the tag. The return value can be iterated over for all
the sectors/lines/things with that tag. The length can also be taken for the
number of such objects. If no argument is given, the global tag is default.

Added support for map names, matched by substring and keywords too!
Added support for two digit MAP codes without the MAP part.
Added support for decimal map number. (But who cares.)

Gave a better description of command.
Supported abbreviated optional parameters.

And now REALLY detects incorrect parameters.

No longer using byte2float in DrawPolygon -- use the surface color data directly
Vertex Buffer Objects for non-interpolated model frames
Removed some old unused paletted texture stuff

* Move the misc types in the file to bottom, so that ATTRPACK at least is usable for RGBA_t
* Include endian.h, so that UINT2RGBA can be defined correctly for big endian builds
* Add more comments to make clear the main sections of the file

Get rid of stack overflow code because filesystem case insensitivity is Windows exlcusive, so we can just create a wrapper function for there instead of rolling our own.

https://gfycat.com/DizzyEnergeticCygnet

I will make it prettier.

(Also: stristr. Since the Windows (and others?) standard library doesn't have it for some reason, I modified code someone put on StackExchange as a stopgap; once I'm ready to get on IRC for the day, we'll discuss attribution/rewriting.)

(no actual SLOC changes)

some of the mess in here really bothers me

(cherry-picking this commit of mine from next since it only fixes a small oversight with compiling and adds a comment)

some of the mess in here really bothers me

some of the mess in here really bothers me

snprintf is now available in MSVC 2015!