install headers in include/minizip to avoid conflicts with libzip

Index: CMakeLists.txt
--- CMakeLists.txt.orig
+++ CMakeLists.txt
@@ -81,7 +81,7 @@ include(FeatureSummary)
 
 set(INSTALL_BIN_DIR ${CMAKE_INSTALL_BINDIR} CACHE PATH "Installation directory for executables")
 set(INSTALL_LIB_DIR ${CMAKE_INSTALL_LIBDIR} CACHE PATH "Installation directory for libraries")
-set(INSTALL_INC_DIR ${CMAKE_INSTALL_INCLUDEDIR} CACHE PATH "Installation directory for headers")
+set(INSTALL_INC_DIR ${CMAKE_INSTALL_INCLUDEDIR}/minizip CACHE PATH "Installation directory for headers")
 set(INSTALL_MAN_DIR ${CMAKE_INSTALL_MANDIR} CACHE PATH "Installation directory for manual pages")
 
 set(STDLIB_DEF)
@@ -449,7 +449,6 @@ endif()
 
 # Unix specific
 if(UNIX)
-    list(APPEND STDLIB_DEF -D_POSIX_C_SOURCE=200112L)
     list(APPEND MINIZIP_SRC mz_os_posix.c mz_strm_os_posix.c)
 
     if(MZ_PKCRYPT OR MZ_WZAES OR MZ_SIGNING)
