Cmake: Build with GSSAPI (MIT or Heimdal)

It tries hard to recognise SDK's on different platforms. On windows MIT
Kerberos installs SDK with other things and puts path into registry.
Heimdal have separate zip archive. On linux pkg-config is tried, then
krb5-config script and finally old-style libs and headers detection.

Command line args:
* CMAKE_USE_GSSAPI - enables GSSAPI detection
* GSS_ROOT_DIR - if set, should point to the root of GSSAPI installation
                 (the one with include and lib directories)

CMakeLists.txt

@@ -416,8 +416,64 @@ if(CMAKE_USE_LIBSSH2)
   endif(LIBSSH2_FOUND)
 endif(CMAKE_USE_LIBSSH2)
 
-# For other tests to use the same libraries
-set(CMAKE_REQUIRED_LIBRARIES ${CURL_LIBS})
+option(CMAKE_USE_GSSAPI "Use GSSAPI implementation (right now only Heimdal is supported with CMake build)" OFF)
+mark_as_advanced(CMAKE_USE_GSSAPI)
+
+if(CMAKE_USE_GSSAPI)
+  find_package(GSS)
+
+  set(HAVE_GSS_API ${GSS_FOUND})
+  if(GSS_FOUND)
+
+    message(STATUS "Found ${GSS_FLAVOUR} GSSAPI version: \"${GSS_VERSION}\"")
+
+    set(CMAKE_REQUIRED_INCLUDES ${GSS_INCLUDE_DIR})
+    check_include_file_concat("gssapi/gssapi.h"  HAVE_GSSAPI_GSSAPI_H)
+    check_include_file_concat("gssapi/gssapi_generic.h" HAVE_GSSAPI_GSSAPI_GENERIC_H)
+    check_include_file_concat("gssapi/gssapi_krb5.h" HAVE_GSSAPI_GSSAPI_KRB5_H)
+
+    if(GSS_FLAVOUR STREQUAL "Heimdal")
+      set(HAVE_GSSHEIMDAL ON)
+    else() # MIT
+      set(HAVE_GSSMIT ON)
+      set(_INCLUDE_LIST "")
+      if(HAVE_GSSAPI_GSSAPI_H)
+        list(APPEND _INCLUDE_LIST "gssapi/gssapi.h")
+      endif()
+      if(HAVE_GSSAPI_GSSAPI_GENERIC_H)
+        list(APPEND _INCLUDE_LIST "gssapi/gssapi_generic.h")
+      endif()
+      if(HAVE_GSSAPI_GSSAPI_KRB5_H)
+        list(APPEND _INCLUDE_LIST "gssapi/gssapi_krb5.h")
+      endif()
+
+      string(REPLACE ";" " " _COMPILER_FLAGS_STR "${GSS_COMPILER_FLAGS}")
+      string(REPLACE ";" " " _LINKER_FLAGS_STR "${GSS_LINKER_FLAGS}")
+
+      foreach(_dir ${GSS_LINK_DIRECTORIES})
+        set(_LINKER_FLAGS_STR "${_LINKER_FLAGS_STR} -L\"${_dir}\"")
+      endforeach()
+
+      set(CMAKE_REQUIRED_FLAGS "${_COMPILER_FLAGS_STR} ${_LINKER_FLAGS_STR}")
+      set(CMAKE_REQUIRED_LIBRARIES ${GSS_LIBRARIES})
+      check_symbol_exists("GSS_C_NT_HOSTBASED_SERVICE" ${_INCLUDE_LIST} HAVE_GSS_C_NT_HOSTBASED_SERVICE)
+      if(NOT HAVE_GSS_C_NT_HOSTBASED_SERVICE)
+        set(HAVE_OLD_GSSMIT ON)
+      endif()
+
+    endif()
+
+    include_directories(${GSS_INCLUDE_DIR})
+    link_directories(${GSS_LINK_DIRECTORIES})
+    set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} ${GSS_COMPILER_FLAGS}")
+    set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} ${GSS_LINKER_FLAGS}")
+    set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} ${GSS_LINKER_FLAGS}")
+    list(APPEND CURL_LIBS ${GSS_LIBRARIES})
+
+  else()
+    message(WARNING "GSSAPI support has been requested but no supporting libraries found. Skipping.")
+  endif()
+endif()
 
 # If we have features.h, then do the _BSD_SOURCE magic
 check_include_file("features.h"       HAVE_FEATURES_H)
@@ -457,9 +513,6 @@ check_include_file_concat("des.h"            HAVE_DES_H)
 check_include_file_concat("err.h"            HAVE_ERR_H)
 check_include_file_concat("errno.h"          HAVE_ERRNO_H)
 check_include_file_concat("fcntl.h"          HAVE_FCNTL_H)
-check_include_file_concat("gssapi/gssapi.h"  HAVE_GSSAPI_GSSAPI_H)
-check_include_file_concat("gssapi/gssapi_generic.h" HAVE_GSSAPI_GSSAPI_GENERIC_H)
-check_include_file_concat("gssapi/gssapi_krb5.h" HAVE_GSSAPI_GSSAPI_KRB5_H)
 check_include_file_concat("idn-free.h"       HAVE_IDN_FREE_H)
 check_include_file_concat("ifaddrs.h"        HAVE_IFADDRS_H)
 check_include_file_concat("io.h"             HAVE_IO_H)
@@ -579,6 +632,12 @@ find_file(RANDOM_FILE urandom /dev)
 mark_as_advanced(RANDOM_FILE)
 
 # Check for some functions that are used
+if(HAVE_LIBWS2_32)
+  set(CMAKE_REQUIRED_LIBRARIES ws2_32)
+elseif(HAVE_LIBSOCKET)
+  set(CMAKE_REQUIRED_LIBRARIES socket)
+endif()
+
 check_symbol_exists(basename      "${CURL_INCLUDES}" HAVE_BASENAME)
 check_symbol_exists(socket        "${CURL_INCLUDES}" HAVE_SOCKET)
 check_symbol_exists(poll          "${CURL_INCLUDES}" HAVE_POLL)
@@ -680,12 +739,7 @@ if(NOT HAVE_STRICMP)
   set(HAVE_LDAP_URL_PARSE 1)
 endif(NOT HAVE_STRICMP)
 
-
-
 # Do curl specific tests
-if(HAVE_LIBWS2_32)
-  set(CMAKE_REQUIRED_LIBRARIES ws2_32)
-endif()
 foreach(CURL_TEST
     HAVE_FCNTL_O_NONBLOCK
     HAVE_IOCTLSOCKET