conf-parser: distinguish between multiple sections with the same name

Pass on the line on which a section was decleared to the parsers, so they
can distinguish between multiple sections (if they chose to). Currently
no parsers take advantage of this, but a follow-up patch will do that
to distinguish

[Address]
Address=192.168.0.1/24
Label=one

[Address]
Address=192.168.0.2/24
Label=two

from

[Address]
Address=192.168.0.1/24
Label=one
Address=192.168.0.2/24
Label=two

src/shared/install.c

@@ -922,6 +922,7 @@ static int config_parse_also(const char *unit,
                              const char *filename,
                              unsigned line,
                              const char *section,
+                             unsigned section_line,
                              const char *lvalue,
                              int ltype,
                              const char *rvalue,
@@ -957,6 +958,7 @@ static int config_parse_user(const char *unit,
                              const char *filename,
                              unsigned line,
                              const char *section,
+                             unsigned section_line,
                              const char *lvalue,
                              int ltype,
                              const char *rvalue,