Issue 360 - Alignment check on in configure.ac is broken and results in addition memcpy()s

### Scope of Change ###
Rewriting of existing alignment check. Merge of previous pull request [#3](https://github.com/memcached/memcached/pull/3), and [Issue 360](https://code.google.com/p/memcached/issues/detail?id=360). 

### Testing Hardware ###
Testing was complete on a G5 PowerPC, running Debian OS.  *Note:* An additional patch was need to allow test suite to complete on system, but has been omitted from commit.

```diff
diff --git a/testapp.c b/testapp.c
index 5a62aca..0aff644 100644
--- a/testapp.c
+++ b/testapp.c
@@ -1037,6 +1037,7 @@ static enum test_return test_binary_quit_impl(uint8_t cmd) {
                                  PROTOCOL_BINARY_RESPONSE_SUCCESS);
     }
 
+    usleep(1); /* let socket catch up */
     /* Socket should be closed now, read should return 0 */
     assert(read(sock, buffer.bytes, sizeof(buffer.bytes)) == 0);
     close(sock);
```

### Testing Evidence ###
Below is a diff between release 1.4.18 (testapp-memcached-1.4.18.log) & this pull request (testapp-memcached-360fix.log). Both executed on the same machine with the above patch applied.
```diff
--- testapp-memcached-1.4.18.log	2014-04-25 00:02:50.294848641 +0000
+++ testapp-memcached-360fix.log	2014-04-25 00:57:39.952546993 +0000
@@ -1,8 +1,8 @@
 ./sizes
 Slab Stats	64
 Thread stats	200
-Global stats	224
-Settings	128
+Global stats	216
+Settings	120
 Item (no cas)	32
 Item (cas)	40
 Libevent thread	104
@@ -62,6 +62,8 @@
 ok 47 - shutdown
 ok 48 - stop_server
 prove ./t
+getaddrinfo(): Name or service not known
+failed to listen on TCP port 42353: Success
 slab class   1: chunk size        80 perslab   13107
 slab class   2: chunk size       104 perslab   10082
 slab class   3: chunk size       136 perslab    7710
@@ -232,8 +234,6 @@
 <36 connection closed.
 Invalid value for binding protocol: http
  -- should be one of auto, binary, or ascii
-getaddrinfo(): Name or service not known
-failed to listen on TCP port 40191: Success
 Number of threads must be greater than 0
 t/00-startup.t ....... ok
 t/64bit.t ............ skipped: Skipping 64-bit tests on 32-bit build
@@ -279,7 +279,6 @@
  and will decrease your memory efficiency.
 t/item_size_max.t .... ok
 t/line-lengths.t ..... ok
-t/lru-crawler.t ...... ok
 t/lru.t .............. ok
 t/maxconns.t ......... ok
 t/multiversioning.t .. ok
@@ -291,18 +290,17 @@
 t/touch.t ............ ok
 t/udp.t .............. ok
 t/unixsocket.t ....... ok
-fatal: Not a git repository (or any of the parent directories): .git
-t/whitespace.t ....... skipped: Skipping tests probably because you don't have git.
+t/whitespace.t ....... ok
 All tests successful.
-Files=48, Tests=7077, 363 wallclock secs (48.72 usr  4.56 sys + 131.10 cusr 40.36 csys = 224.74 CPU)
+Files=47, Tests=6986, 368 wallclock secs (52.89 usr  4.79 sys + 137.09 cusr 40.06 csys = 234.83 CPU)
 Result: PASS
 File 'assoc.c' Lines executed:44.44% of 117 
 File 'cache.c' Lines executed:53.33% of 75 
 File 'daemon.c' Lines executed:9.09% of 22 
 File 'hash.c' Lines executed:62.50% of 8 
-File 'items.c' Lines executed:82.63% of 518 
+File 'items.c' Lines executed:85.76% of 316 
 File 'jenkins_hash.c' Lines executed:100.00% of 56 
-File 'memcached.c' Lines executed:70.54% of 2695 
+File 'memcached.c' Lines executed:71.22% of 2627 
 File 'murmur3_hash.c' Lines executed:0.00% of 32 
 File 'slabs.c' Lines executed:70.98% of 410 
 File 'stats.c' Lines executed:90.36% of 83 
```