Support building PHP with the native client toolchain.

The native client compiler defines the C macro __x86_64__, but the size
of an unsigned int is only 4 bytes. This causes the compile to fail
because the inline asm code compiled is for an 8 byte unsigned int. Add
the correct defines to fix this.

As detailed in:
http://code.google.com/p/nativeclient/issues/detail?id=2255

Author: sjlangley

Zend/zend_alloc.c

@@ -664,7 +664,7 @@ static void *_zend_mm_realloc_int(zend_mm_heap *heap, void *p, size_t size ZEND_
 
 static inline unsigned int zend_mm_high_bit(size_t _size)
 {
-#if defined(__GNUC__) && defined(i386)
+#if defined(__GNUC__) && (defined(__native_client__) || defined(i386))
 	unsigned int n;
 
 	__asm__("bsrl %1,%0\n\t" : "=r" (n) : "rm"  (_size));
@@ -690,7 +690,7 @@ static inline unsigned int zend_mm_high_bit(size_t _size)
 
 static inline unsigned int zend_mm_low_bit(size_t _size)
 {
-#if defined(__GNUC__) && defined(i386)
+#if defined(__GNUC__) && (defined(__native_client__) || defined(i386))
 	unsigned int n;
 
 	__asm__("bsfl %1,%0\n\t" : "=r" (n) : "rm"  (_size));
@@ -2454,7 +2454,7 @@ ZEND_API size_t _zend_mem_block_size(void *ptr TSRMLS_DC ZEND_FILE_LINE_DC ZEND_
 	return _zend_mm_block_size(AG(mm_heap), ptr ZEND_FILE_LINE_RELAY_CC ZEND_FILE_LINE_ORIG_RELAY_CC);
 }
 
-#if defined(__GNUC__) && defined(i386)
+#if defined(__GNUC__) && (defined(__native_client__) || defined(i386))
 
 static inline size_t safe_address(size_t nmemb, size_t size, size_t offset)
 {