Clean up CMake header and type checks.

Unused macros: HAVE_DLFCN_H, HAVE_INTTYPES_H, HAVE_MEMORY_H,
HAVE_STDLIB_H, HAVE_STRINGS_H, HAVE_STRING_H, HAVE_SYS_BYTESWAP_H,
HAVE_SYS_STAT_H, HAVE_SYS_TYPES_H, HAVE_UNISTD_H.

Used but never set macros: HAVE_LIBLZF, HAVE_LIBQUICKLZ. These only gate
conditional includes. The code that takes advantage of them was removed.

Unused types: ssize_t.

The testing code uses HAVE_FUNC_MMAP, which was not wired in the CMake
build, causing a whole test to be skipped.

CMakeLists.txt

@@ -6,6 +6,7 @@ SET(CMAKE_INCLUDE_CURRENT_DIR ON)
 INCLUDE(CheckIncludeFiles)
 INCLUDE(CheckLibraryExists)
 INCLUDE(CheckCXXSourceCompiles)
+INCLUDE(CheckSymbolExists)
 INCLUDE(TestBigEndian)
 INCLUDE(CMakePackageConfigHelpers)
 
@@ -16,23 +17,13 @@ IF (WORDS_BIG_ENDIAN)
 ENDIF (WORDS_BIG_ENDIAN)
 
 CHECK_INCLUDE_FILES("byteswap.h" HAVE_BYTESWAP_H)
-CHECK_INCLUDE_FILES("dlfcn.h" HAVE_DLFCN_H)
-CHECK_INCLUDE_FILES("inttypes.h" HAVE_INTTYPES_H)
-CHECK_INCLUDE_FILES("memory.h" HAVE_MEMORY_H)
 CHECK_INCLUDE_FILES("stddef.h" HAVE_STDDEF_H)
 CHECK_INCLUDE_FILES("stdint.h" HAVE_STDINT_H)
-CHECK_INCLUDE_FILES("stdlib.h" HAVE_STDLIB_H)
-CHECK_INCLUDE_FILES("strings.h" HAVE_STRINGS_H)
-CHECK_INCLUDE_FILES("string.h" HAVE_STRING_H)
-CHECK_INCLUDE_FILES("sys/byteswap.h" HAVE_SYS_BYTESWAP_H)
 CHECK_INCLUDE_FILES("sys/endian.h" HAVE_SYS_ENDIAN_H)
 CHECK_INCLUDE_FILES("sys/mman.h" HAVE_SYS_MMAN_H)
 CHECK_INCLUDE_FILES("sys/resource.h" HAVE_SYS_RESOURCE_H)
-CHECK_INCLUDE_FILES("sys/stat.h" HAVE_SYS_STAT_H)
 CHECK_INCLUDE_FILES("sys/time.h" HAVE_SYS_TIME_H)
-CHECK_INCLUDE_FILES("sys/types.h" HAVE_SYS_TYPES_H)
 CHECK_INCLUDE_FILES("sys/uio.h" HAVE_SYS_UIO_H)
-CHECK_INCLUDE_FILES("unistd.h" HAVE_UNISTD_H)
 CHECK_INCLUDE_FILES("windows.h" HAVE_WINDOWS_H)
 
 IF (NOT HAVE_SYS_UIO_H)
@@ -50,6 +41,8 @@ ENDIF (NOT HAVE_STDDEF_H)
 CHECK_LIBRARY_EXISTS(z zlibVersion "" HAVE_LIBZ)
 CHECK_LIBRARY_EXISTS(lzo2 lzo1x_1_15_compress "" HAVE_LIBLZO2)
 
+CHECK_SYMBOL_EXISTS(mmap sys/mman.h HAVE_FUNC_MMAP)
+
 CHECK_CXX_SOURCE_COMPILES("int main(void) { return __builtin_expect(0, 1); }"
         HAVE_BUILTIN_EXPECT)
 
@@ -136,14 +129,6 @@ IF (HAVE_LIBLZO2)
     LIST(APPEND COMPRESSION_LIBS lzo2)
 ENDIF (HAVE_LIBLZO2)
 
-IF (HAVE_LIBLZF)
-    LIST(APPEND COMPRESSION_LIBS lzf)
-ENDIF (HAVE_LIBLZF)
-
-IF (HAVE_LIBQUICKLZ)
-    LIST(APPEND COMPRESSION_LIBS quicklz)
-ENDIF (HAVE_LIBQUICKLZ)
-
 ADD_EXECUTABLE(snappy-unittest snappy_unittest.cc snappy-test.cc)
 TARGET_COMPILE_DEFINITIONS(snappy-unittest PRIVATE -DHAVE_CONFIG_H)
 TARGET_LINK_LIBRARIES(snappy-unittest snappy ${COMPRESSION_LIBS}