Build for iOS (device) fails due to no crt_extern

[nsands]

Building GDAL 1.10 for iOS (device) fails due to no crt_extern on iOS. Note that it builds OK for the iOS simulator, but not for the device. The build error is included below, but the following fixed this error. In file 'cpl_spawn.cpp' Replace:

#ifdef __APPLE__
#include <crt_externs.h>

With:

#ifdef __APPLE__
# include <TargetConditionals.h>
#endif
#if defined(__APPLE__) && !defined(TARGET_OS_IPHONE)
#include <crt_externs.h>

For completeness, the error output before this change was:

libtool: compile: 
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Dev
eloper/usr/bin/g++ -arch armv7 -pipe -Os -gdwarf-2 -isysroot
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Dev
eloper/SDKs/iPhoneOS6.1.sdk -mno-thumb -mthumb-interwork -Wall
-DOGR_ENABLED -I/Users/nsands/Documents/Nik/Development/gdal-1.10.0/port
-DHAVE_LIBZ -I/usr/include/libxml2 -DHAVE_LIBXML2 -c cpl_spawn.cpp -o
cpl_spawn.o cpl_spawn.cpp:465:25: error: crt_externs.h: No such file or
directory cpl_spawn.cpp: In function 'CPLSpawnedProcess* CPLSpawnAsync(int
(*)(CPL_FILE_HANDLE, CPL_FILE_HANDLE), const char* const*, int, int, int,
char**)': cpl_spawn.cpp:727: error: '_NSGetEnviron' was not declared in
this scope make[1]: *** [cpl_spawn.lo] Error 1
make: *** [port-target] Error 2