rpmspec: add make_install, make_build keywords

%make_install added in RPM 4.8[0]
%make_build added in RPM 4.12[1]

[0]http://rpm.org/gitweb?p=rpm.git;a=commitdiff;h=883253ea6af71f8063d7a045841c35bad22147e2
[1]http://rpm.org/gitweb?p=rpm.git;a=commitdiff;h=89df36524bace71decee4ab4f979d4ffb449c9a7

Signed-off-by: Igor Gnatenko <i.gnatenko.brain@gmail.com>
build: "core" helper library for unit tests

The "private" helper library contained only the private classes. But
when a private class needs a symbol from the public classes, there can
be some linking problems.

There is a simpler solution, have all the classes (public and private)
in a "core" helper library. When unit tests link to this core library,
they can use private symbols.
File loading and saving

New public classes: GtkSourceEncoding, GtkSourceFile,
GtkSourceFileLoader and GtkSourceFileSaver.

https://bugzilla.gnome.org/show_bug.cgi?id=721016
Make sure text passed to insert_text is null terminated

Based on Jesse's commit d50108e57935871125cb42f275ebc2f096448452 in
gedit.

https://bugzilla.gnome.org/show_bug.cgi?id=726390