Servertalk implementation wip, added optional support for pub-key authenticated encryption (via libsodium), not backwards compatible.

cmake/FindSodium.cmake

@@ -0,0 +1,30 @@
+if (NOT MSVC)
+include(FindPkgConfig)
+pkg_check_modules(PC_SODIUM "libsodium")
+if (NOT PC_SODIUM_FOUND)
+    pkg_check_modules(PC_SODIUM "sodium")
+endif (NOT PC_SODIUM_FOUND)
+if (PC_SODIUM_FOUND)
+  set(SODIUM_INCLUDE_HINTS ${PC_SODIUM_INCLUDE_DIRS} ${PC_SODIUM_INCLUDE_DIRS}/*)
+  set(SODIUM_LIBRARY_HINTS ${PC_SODIUM_LIBRARY_DIRS} ${PC_SODIUM_LIBRARY_DIRS}/*)
+endif()
+endif (NOT MSVC)
+
+# some libraries install the headers is a subdirectory of the include dir
+# returned by pkg-config, so use a wildcard match to improve chances of finding
+# headers and libraries.
+find_path(
+    SODIUM_INCLUDE_DIRS
+    NAMES sodium.h
+    HINTS ${SODIUM_INCLUDE_HINTS}
+)
+
+find_library(
+    SODIUM_LIBRARIES
+    NAMES libsodium sodium
+    HINTS ${SODIUM_LIBRARY_HINTS}
+)
+
+include(FindPackageHandleStandardArgs)
+find_package_handle_standard_args(SODIUM DEFAULT_MSG SODIUM_LIBRARIES SODIUM_INCLUDE_DIRS)
+mark_as_advanced(SODIUM_FOUND SODIUM_LIBRARIES SODIUM_INCLUDE_DIRS)