postgresql: adding --universal support.

This adds ``universal`` support to the ``postgresql`` formula.

This applies a **post-configure** patch to fix headers created in the configure process, changing lines such as:

```c
/* The normal alignment of `double', in bytes. */
#define ALIGNOF_DOUBLE 8
```

To lines like this:

```c
/* The normal alignment of `double', in bytes. */
#ifdef __LP64__
#define ALIGNOF_DOUBLE 8
#else
#define ALIGNOF_DOUBLE 4
#endif
```

This uses the same approach used by MacPorts, but instead of applying an ``ed`` script, uses ``ruby`` to make the string substitutions.

For more background information, see the related requests and discussions for this feature: #1325, #14032, #14036, #14111, #14616, and #14775.