pgsql: Sort $(wildcard) output where needed for reproducible build outp

Sort $(wildcard) output where needed for reproducible build output.

The order of inclusion of .o files makes a difference in linker output;
not a functional difference, but still a bitwise difference, which annoys
some packagers who would like reproducible builds.

Report and patch by Christoph Berg

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/8805af0886c671adcaf0200d70549d5d933f5cf2

Modified Files
--------------
contrib/hstore_plperl/Makefile   |    2 +-
contrib/hstore_plpython/Makefile |    4 ++--
contrib/ltree_plpython/Makefile  |    4 ++--
src/bin/pg_xlogdump/Makefile     |    2 +-
4 files changed, 6 insertions(+), 6 deletions(-)