trac#408: ./configure --enable-valgrind should fail when valgrind command was not found
Merge pull request #14 from jan-cerny/master

Plug a memory leak.
Merge pull request #15 from jan-cerny/conffail

trac#408: ./configure --enable-valgrind should fail when valgrind comman...
Refactor: Extract function: save_stylesheet_result_to_file.
Free XSLT arguments immediatelly.
Refactor: Extract function: apply_xslt_path_internal.
Introduce: oscap_source_apply_xslt_path_mem.
Introduce ds_rds_session.
Introduce: ds_rds_session_get_html_report.
trac#411: Remove references to docbook feature