(frontend.c) Fix include
(Nearest Resampler) C89 build fixes
Merge pull request #1024 from lakkatv/lakka

(Lakka) Display a black background if no png background supplied
Merge pull request #1023 from heuripedes/frontend

(frontend.c) Fix include
Split up driver_menu.h into three separate header files -
for menu display API, menu backend API, and menu driver general API
Move audio_frame_float typedef struct to resampler.h
Silence warning 'variable is used before its value is set'
Don't rely on retro_time_t typedef for menu_driver API
(Lakka) Fixes
(d3d_ctx.cpp) Add HAVE_EGL check
(string_list.c) Include posix_string.h
Merge pull request #1025 from heuripedes/master

Windows builds fixes
Fix xinput autoconfig support in MSYS2 builds
Make sure SDL1 is disabled when SDL2 is active
(Makefile) Pass -static-libgcc to the linker on Win32
Merge pull request #1026 from heuripedes/master

More Windows fixes
(Menu) Don't need menu_type_is anymore in menu display drivers
Cleanups
Take out frame_buf_show in menu_driver.h
rpng.c - cleanup