Native 64-bit Linux build

This adds native linux 64-bit supports. Tested with github/rebol-test, three progressions and no regression agains master 32-bit found:

```diff
--- r_2_101_0_4_4_22C633_4E5726.log	2013-08-31 10:01:12.003341307 -0400
+++ r_2_101_0_4_40_183F68_4E5726.log	2013-08-28 09:39:34.563339334 -0400
@@ -4849,13 +4849,13 @@
 [0.1 == round/half-down/to 0.15 0.1] "succeeded"
 [0.2 == round/half-down/to 0.15001 0.1] "succeeded"
 [0.5 == round/half-down/to 0.55 0.1] "succeeded"
-[0.6 == round/half-down/to 0.55001 0.1] "failed"
+[0.6 == round/half-down/to 0.55001 0.1] "succeeded"
 [0.5 == round/half-down/to 0.75 0.5] "succeeded"
 [1.0 == round/half-down/to 0.75001 0.5] "succeeded"
 [-0.1 == round/half-down/to -0.15 0.1] "succeeded"
 [-0.2 == round/half-down/to -0.15001 0.1] "succeeded"
 [-0.5 == round/half-down/to -0.55 0.1] "succeeded"
-[-0.6 == round/half-down/to -0.55001 0.1] "failed"
+[-0.6 == round/half-down/to -0.55001 0.1] "succeeded"
 [-0.5 == round/half-down/to -0.75 0.5] "succeeded"
 [-1.0 == round/half-down/to -0.75001 0.5] "succeeded"
 [0 = sign? 0] "succeeded"
@@ -5825,7 +5825,7 @@
 	error? try blk
 ] "succeeded"
 [error? try [apply 'type?/word []]] "succeeded"
-[same? :add attempt [apply does [return/redo :add] []]] "failed"
+[same? :add attempt [apply does [return/redo :add] []]] "succeeded"
 [2 == do does [return apply :do [:add 1 1] 4 4]] "failed"
 [1 == apply :subtract [2 1]] "succeeded"
 [1 == apply :- [2 1]] "succeeded"
@@ -8463,12 +8463,12 @@
 ] "failed, error was caused in the test code"
 [equal? read write clipboard:// c: "test" c] "failed, error was caused in the test code"
 
-system/version: 2.101.0.4.4
-code-checksum: #{22C633E24BFD4FDBE04A6098E41BD954C3B7D04C}
+system/version: 2.101.0.4.40
+code-checksum: #{183F684918FA91FE87D599821E541D30651FBE9D}
 test-checksum: #{4E5726B3CE4645AC5EAB8AF08F677090E0998DD3}
 Total: 4696
-Succeeded: 4211
-Test-failures: 161
+Succeeded: 4214
+Test-failures: 158
 Crashes: 16
 Dialect-failures: 0
 Skipped: 308
```