Stall testing for interpolation

Uncapped framerate never triggered the stall detection code, as it never
tried to process a frame to start with.
Merge branch 'master' of https://github.com/Edward850/zdoom
- Add support for cross compiling so that OS X PowerPC builds can still be made on systems without rosetta (10.7+). (Compiling x86 binaries on ppc should also be possible.)
- Hard code gdtoa constants for OS X since the programs can’t always be run on the target.  (The values are the same for GCC and Clang.)
- Work around GCC 4.8 bug 54570
- Work around GCC 4.8 bug 54570
Merge branch 'maint'
- Fixed: Rampage timer should only reset when the weapon is ready to be fired.
- So we did end up restoring the variable that the last commit was compensating for.
- Updated gdtoa in order to fix clang warnings.
- Fixed: SBarInfo's gamemode command used to ignore unknowns (for cross compatibility). On top of restoring the old behavior, generate a warning for only the first ignored instance.
- Fixed: All clang 5.0 warnings.
- Renamed autostart/autozend since Xcode’s build process links in strictly alphabetical order.
Merge commit 'b3f5de356f14e2026cc9e5738e8b58e22e7daa44'
- For some reason __MAC_10_6 is defined in the 10.5 SDK so use MAC_OS_X_VERSION_MAX to check SDK version instead.
- Ignore unknown properties in the GAMEINFO lump instead of throwing an error.
Merge branch 'origin/maint'
Treat packets from unknown nodes differently

Instead of trying to decompress packets from unknown connections (and
failing them anyway), they are now reported and discarded without doing
anything else.
Merge branch 'master' of https://github.com/Edward850/zdoom
- removed all unneeded files from gdtoa/CMakeLists.txt because some compilers seem to throw duplicate symbol errors when strtod gets included.
Fixed signed overflow issue, which caused a non-intended aggressive optimization by GCC 4.8. Also, negative values of the 'limit' parameter in both ACS UniqueTID() and in 'utid' CCMD are ignored and replaced by 0.