According to a comment from Kreeblah[1], homebrew guarantees a new
enough C++ compiler. Additionally, gcc5 was once new enough, but is now
below the minimum supported version, so installing it is not useful.
Remove the reference to it.
[1]: https://github.com/dxx-rebirth/dxx-rebirth/pull/540#discussion_r486059009
Support for ORTHO_VIEWS has been broken since commit
db514a5ded in December 2004.
`git blame HEAD -L872,+4 -- similar/editor/meddraw.cpp`:
```
db514a5ded main/editor/meddraw.c (Bradley Bell 2004-12-19 13:54:27 +0000 872) }
db514a5ded main/editor/meddraw.c (Bradley Bell 2004-12-19 13:54:27 +0000 873) } else
db514a5ded main/editor/meddraw.c (Bradley Bell 2004-12-19 13:54:27 +0000 874) #if ORTHO_VIEWS
db514a5ded main/editor/meddraw.c (Bradley Bell 2004-12-19 13:54:27 +0000 875) else if ( screen_canvas == TopViewBox->canvas )
```
When ORTHO_VIEWS is true, this code expands to `} else else if (...)`; a
double-else is not legal, so the code cannot have been compiled with
ORTHO_VIEWS enabled. All 4 of the relevant lines date to db514a5ded,
which itself is an import of files from the D1X editor.
Rebirth built with OpenGL has a hard dependency on the GL utility
library, but did not have a configure time test to report this. Add
one.
Reported-by: shoober420 <https://github.com/dxx-rebirth/dxx-rebirth/issues/468>
When joystick support is not present, `event_joystick_get_button` is not
declared in joy.h.
Fixes: c24864b180 ("make menus controllable with joystick")
The same logic is used in two places. Move it to a helper function, and
switch from repeated use of snprintf for one character at a time to
instead use fill_n.
Check if the cockpit window textures are still valid when reusing the
previous cockpit data in cockpit_decode_alpha.
This fixes a crash when leaving the graphics options menu while in
the game with cockpit visible, since that calls
ogl_smash_texture_list_internal which invalidates all textures.
