Fix the usage of posix_fallocate() so that it correctly responds to

EINVAL returns.

FossilOrigin-Name: ce2c3e7a875ede4366c48660ae8239d2b74e5f690ad5059844a45f1164f41e61

manifest

@@ -1,5 +1,5 @@
-C Update\sa\stest\scase\sin\smalloc5.test\sto\stake\sinto\saccount\sthat\smalloc()\nsometimes\sreturns\sslightly\smore\sspace\sthan\srequested.
-D 2018-06-02T17:00:57.712
+C Fix\sthe\susage\sof\sposix_fallocate()\sso\sthat\sit\scorrectly\sresponds\sto\nEINVAL\sreturns.
+D 2018-06-02T19:01:54.408
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F Makefile.in bfc40f350586923e0419d2ea4b559c37ec10ee4b6e210e08c14401f8e340f0da
@@ -479,7 +479,7 @@ F src/os.c 1cb0d1d1b3a4267966dee6e292d2b2cdf88e47c0c59cebff27ecafac052dd165
 F src/os.h 48388821692e87da174ea198bf96b1b2d9d83be5dfc908f673ee21fafbe0d432
 F src/os_common.h b2f4707a603e36811d9b1a13278bffd757857b85
 F src/os_setup.h 0dbaea40a7d36bf311613d31342e0b99e2536586
-F src/os_unix.c 2b53b0b8ddc580db096252c721729e5f5f2f355b4fc056f8f3fb328aeb3c9e8a
+F src/os_unix.c c230a7a24766320d8414afd087edcd43e499fb45e86361f6f4f464f343d965a9
 F src/os_win.c ac29c25cde4cfb4adacc59cdec4aa45698ca0e29164ea127859585ccd9faa354
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
 F src/pager.c 1bb6a57fa0465296a4d6109a1a64610a0e7adde1f3acf3ef539a9d972908ce8f
@@ -1730,7 +1730,8 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P e336cf00486bdc0ec04ecded2b7c874d73a87e6aba3544e3678bedfb9a4af3b6
-R 6e46205cb0ef6ad7de1d5ad2d4fadd35
-U dan
-Z ef3783ba7b32ff9195245e676b3fce8c
+P 3d5eae1c26353cdee89f31f1293b05c0edb494c775ba0912d9b4fda9ab0ef304 ab3a5539db82814cafb832cdaebd1e14566139306453ef9cdba6b244a994fe0b
+R 64e7a20d51f9d1438ac9592daa9dd6bf
+T +closed ab3a5539db82814cafb832cdaebd1e14566139306453ef9cdba6b244a994fe0b
+U drh
+Z 8bf90c20199723dfc867a912d22476ec