pgsql: Move gramparse.h to src/backend/parser

Move gramparse.h to src/backend/parser

This header is semi-private, being used only in files related to
raw parsing, so move to the backend directory where those files
live. This allows removal of Makefile rules that symlink gram.h to
src/include/parser, since gramparse.h can now include gram.h from
within the same directory. This has the side-effect of no longer
installing gram.h and gramparse.h, but there doesn't seem to be a
good reason to continue doing so.

Per suggestion from Andres Freund and Peter Eisentraut
Discussion: https://www.postgresql.org/message-id/20220904181759.px6uosll6zbxcum5%40awork3.anarazel.de

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ecaf7c5df54f7fa9df2fdc7225d2bb4e283f0081

Modified Files
--------------
src/backend/Makefile | 7 +------
src/backend/parser/gram.y | 2 +-
src/{include => backend}/parser/gramparse.h | 4 ++--
src/backend/parser/parser.c | 2 +-
src/backend/parser/scan.l | 2 +-
src/include/Makefile | 4 ++--
src/include/parser/.gitignore | 1 -
src/tools/msvc/Install.pm | 4 ----
src/tools/pginclude/cpluspluscheck | 1 -
src/tools/pginclude/headerscheck | 1 -
10 files changed, 8 insertions(+), 20 deletions(-)