Merge pull request #985 from Sailsman63/64b_static_zlib

Building own zlib on 64bit Linux shared library requires -fPIC for C compiler.

CMakeLists.txt

@@ -164,6 +164,7 @@ ENDIF()
 IF((CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX) AND NOT CMAKE_COMPILER_IS_MINGW)
   IF (BUILD_SHARED_LIBS AND CMAKE_SIZEOF_VOID_P EQUAL 8) # -fPIC is only required for shared libs on 64 bit
      SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fPIC")
+     SET(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -fPIC")
   ENDIF()
   # hide all not-exported symbols
   SET(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fvisibility=hidden -Wall -std=c++0x" )