xapi: Set OCAMLRUNPARAM to enable backtraces

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #116 from euanh/openstack-fixes

xapi: Set OCAMLRUNPARAM to enable backtraces
Warn the user not to call their user "mock"

Added some text pointing at "mock" install instructions.

Using "<user>" "mock" gives a confusing error message:
```
[root@st30 ~]# useradd mock -G mock
useradd: group mock exists - if you want to add this user to that group, use -g.
```
configure: Initialize the repository in RPMS

This is not needed on Fedora, but is needed on ancient CentOS.

Fixes #117

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #118 from euanh/build-improvements

configure: Initialize the repository in RPMS
readme: Fix quotes around <user> in setup instructions

Should be backticks, not double quotes