Also add a debug flag for Reinhard.

Avoid asserting and simply clamping to deal with broken EDIDs like
on LG OLED panels for now.

Needed for fallback surface.

I need to write some wrapper here, this crappy xcb api is rife for errors liek this.

Oops!

DragonFly and FreeBSD adopted a similar API to Linux. Other sytems
maybe interested as well, so add a warning.

src/steamcompmgr.cpp:51:10: fatal error: 'sys/prctl.h' file not found
 #include <sys/prctl.h>
         ^~~~~~~~~~~~~
src/steamcompmgr.cpp:3118:9: error: use of undeclared identifier 'PR_SET_CHILD_SUBREAPER'
        prctl( PR_SET_CHILD_SUBREAPER, 1, 0, 0, 0 );
               ^

On BSD systems only the super-user may lower priority values.

meson.build:40:0: ERROR: Dependency "libcap" not found, tried pkgconfig and cmake

src/main.cpp:7:10: fatal error: 'sys/capability.h' file not found
 #include <sys/capability.h>
          ^~~~~~~~~~~~~~~~~~
src/main.cpp:244:2: error: unknown type name 'cap_t'
        cap_t caps = cap_get_proc();
        ^
src/main.cpp:244:15: error: use of undeclared identifier 'cap_get_proc'
        cap_t caps = cap_get_proc();
                     ^
src/main.cpp:247:3: error: unknown type name 'cap_flag_value_t'
                cap_flag_value_t nicecapvalue = CAP_CLEAR;
                ^
src/main.cpp:247:35: error: use of undeclared identifier 'CAP_CLEAR'
                cap_flag_value_t nicecapvalue = CAP_CLEAR;
                                                ^
src/main.cpp:248:23: error: use of undeclared identifier 'CAP_SYS_NICE'
                cap_get_flag( caps, CAP_SYS_NICE, CAP_EFFECTIVE, &nicecapvalue );
                                    ^
src/main.cpp:248:37: error: use of undeclared identifier 'CAP_EFFECTIVE'
                cap_get_flag( caps, CAP_SYS_NICE, CAP_EFFECTIVE, &nicecapvalue );
                                                  ^
src/main.cpp:250:24: error: use of undeclared identifier 'CAP_SET'
                if ( nicecapvalue == CAP_SET )
                                     ^

… output

Avoids regressing things

…nd it isn't blacklisted for this app

Exposes whether HDR output is currently enabled.