cmake: bump minimum required CMake version to 3.16

main features:

- No more sdl-build-options/sdl-shared-build-options/sdl-global-options
- Dependency information is stored on SDL3-collector for sdl3.pc
- Use helper functions to modify the SDL targets;
    - sdl_sources to add sources
    - sdl_glob_sources to add glob soruces
    - sdl_link_dependency to add a link dependency that might also
      appear in sdl3.pc/SDL3Config.cmake
    - sdl_compile_definitions to add macro's
    - sdl_compile_options for compile options
    - sdl_include_directories for include directories
  They avoid repeated checks for existence of the SDL targets
- A nice feature of the previous is the ability to generate
  a sdl3.pc or SDL3Config.cmake that describes its dependencies
  accurately.

various:

- remove duplicate libc symbol list
- add CheckVulkan
- remove unused HAVE_MPROTECT
- add checks for getpagesize

cmake/PkgConfigHelper.cmake

@@ -0,0 +1,39 @@
+# Helper for Find modules
+
+function(get_flags_from_pkg_config _library _pc_prefix _out_prefix)
+  if("${_library}" MATCHES "${CMAKE_STATIC_LIBRARY_SUFFIX}$")
+    set(_include_dirs ${_pc_prefix}_STATIC_INCLUDE_DIRS)
+    set(_cflags ${_pc_prefix}_STATIC_CFLAGS_OTHER)
+    set(_link_libraries ${_pc_prefix}_STATIC_LIBRARIES)
+    set(_link_options ${_pc_prefix}_STATIC_LDFLAGS_OTHER)
+    set(_library_dirs ${_pc_prefix}_STATIC_LIBRARY_DIRS)
+  else()
+    set(_include_dirs ${_pc_prefix}_INCLUDE_DIRS)
+    set(_cflags ${_pc_prefix}_CFLAGS_OTHER)
+    set(_link_libraries ${_pc_prefix}_LIBRARIES)
+    set(_link_options ${_pc_prefix}_LDFLAGS_OTHER)
+    set(_library_dirs ${_pc_prefix}_LIBRARY_DIRS)
+  endif()
+
+  # The *_LIBRARIES lists always start with the library itself
+  list(POP_FRONT "${_link_libraries}")
+
+  # Work around CMake's flag deduplication when pc files use `-framework A` instead of `-Wl,-framework,A`
+  string(REPLACE "-framework;" "-Wl,-framework," "_filtered_link_options" "${${_link_options}}")
+
+  set(${_out_prefix}_include_dirs
+      "${${_include_dirs}}"
+      PARENT_SCOPE)
+  set(${_out_prefix}_compile_options
+      "${${_cflags}}"
+      PARENT_SCOPE)
+  set(${_out_prefix}_link_libraries
+      "${${_link_libraries}}"
+      PARENT_SCOPE)
+  set(${_out_prefix}_link_options
+      "${_filtered_link_options}"
+      PARENT_SCOPE)
+  set(${_out_prefix}_link_directories
+      "${${_library_dirs}}"
+      PARENT_SCOPE)
+endfunction()