pgsql: Remove USE_VPATH make variable from PGXS

Remove USE_VPATH make variable from PGXS

The user can just set VPATH directly.  There is no need to invent
another variable.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/eb1c3f478645cbbd39877c2a8432f2f8c722eed2

Modified Files
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doc/src/sgml/extend.sgml |    6 +++---
src/makefiles/pgxs.mk    |    9 ++++-----
2 files changed, 7 insertions(+), 8 deletions(-)