Use Automake noinst_HEADERS to list GParted header files

Using Automake variable EXTRA_DIST [1] to list the GParted header files
seems overly general.  Instead use noinst_HEADERS [2] as it better
describes GParted header files.  Header files which need to be
distributed in the archive, but not part of an installed library so not
to be installed below /usr/include.

[1] GNU Automake manual, 14.1 Basics of Distribution
    https://www.gnu.org/software/automake/manual/html_node/Basics-of-Distribution.html
        "..., it is still common to have files to be distributed which
        are not found by the automatic rules.  You should listed these
        files in the EXTRA_DIST variable.  You can mention files in
        subdirectories in EXTRA_DIST.
        "

[2] GNU Automake manual, 9.2 Header files
    https://www.gnu.org/software/automake/manual/html_node/Headers.html
        "Usually, only header files that accompany installed libraries
        need to be installed.  Headers used by programs or convenience
        libraries are not installed.  The noinst_HEADERS variable can be
        used for such headers.  However, when the header belongs to a
        single convenience library or program, we recommend listing it
        in the program's or library's _SOURCES variable (see Defining
        program sources) instead of in noinst_HEADERS.  This is clearer
        for the Makefile.am reader.  noinst_HEADERS would be the right
        variable to use in a directory containing only headers and no
        associated library or program.

        All header files must be listed somewhere; in a _SOURCES
        variable or in a _HEADERS variable.  Missing ones will not
        appear in the distribution.
        "

include/Makefile.am

@@ -1,6 +1,6 @@
 gparted_includedir = $(pkgincludedir)
 
-EXTRA_DIST = \
+noinst_HEADERS = \
 	BCache_Info.h			\
 	BlockSpecial.h			\
 	CopyBlocks.h			\