Force reading of VAR and GISRC files in libgis

[huhabla]

I would like to extent the GIS library environment variable management to support the re-reading of the environment (gisrc and VAR files) in libgis. At the moment this is not possible, environmental files are only read into memory at initialization time. Hence, the reading of environmental variable from different mapsets in the same process is not possible.

I have attached a patch that introduces two new functions to force the reading of env files and a patch that implements the according tests using the gunittest testsuite.

I would like to commit the changes next week if there are no objections. This modification is fundamental to allow distributed temporal databases, so that they are by default created in the current mapsets.

[huhabla]

I have applied the patches in revision r61956 and r61957.

[neteler]

Milestone renamed