Matt Harbison <matt_harbison@yahoo.com> [Fri, 09 Jun 2017 23:56:50 -0400] rev 32757
test-extension: fix load path for Windows
The previous code was trying to load the extension from /tmp/hgtests.xxx/...,
but the actual path for tests is C:\Users\...\Temp\hgtests.xxx\... I assume
that the former is an MSYS path that maps somewhere under C:\MinGW.