hexen: Fix incorrect size on M_StringCopy().

The size parameter for the destination buffer used for this string
copy was one character too short, the result being that patch lump
names using the maximum length (8 characters) were having the last
character cropped off. This in turn caused problems with custom
WADs that added new textures with names like these: the game would
exit on startup with a message like:

  R_InitTextures: Missing patch in texture SKY3GOLD

Amazingly this bug was not noticed because most of the patches in
the Hexen IWAD file have short names of 7 characters or less. The
only exception I noticed was SKYWALL2 which maps to SKYWALL,
another patch, hiding the bug.

Thanks to ETTiNGRiNDER for reporting this bug to me and for
providing me with a private copy of his in-development PWAD that I
could use to find the problem.
hexen: Store minotaur start time as little endian.

The minotaur uses the first four bytes of the mobj_t args[] array to
store its spawn time; after a certain amount of time has passed the
minotaur self-destructs. But the level time was being copied from the
leveltime variable without any endian conversion taking place. For
compatibility with Vanilla Hexen savegames we need to store the start
time in little endian format.

This fixes the first issue noted in #477 (thanks Quasar).
hexen: audit calls to P_StartACS().

Scripts can have a maximum of three arguments when started
(see ACS_Execute / #80 linedef special type). This means that the
array of arguments passed must be at least three elements in
length. When loading scripts, check the argument count never
exceeds 3, and print a warning message if it does.

Don't pass pointers to structure members implicitly treating them
as elements of an array (as this relies on compiler-dependent
behavior as to how structure members are laid out). Instead, copy
values into a temporary array to make the intended behavior explicit.

This fixes #477. Thanks to Quasar for reporting it.
textscreen: Exit immediately when all windows close.

The main loop should exit when the last window closes, but the loop
code was waiting for one event to be received before this took
effect.

This fixes #474. Thanks to Alexandre-Xavier for the report.
Add Steam IWAD path for Strife: Veteran Edition
Merge pull request #481 from chungy/master

Add Steam IWAD path for Strife: Veteran Edition
Upstream fix from SVE: Missing break statement

This caused Rowan to fail to take Beldin's ring from you, if and only if
you had full bullet ammo. Transcription error from the disassembly.
Upstream fix from SVE: MF_MVIS flag

The MVIS flag, if set on an object *without* MF_SHADOW, imparts total
invisibility. This is the intended effect on players using double Shadow
Armors.
Merge branch 'master' of https://github.com/chocolate-doom/chocolate-doom