pgsql: Use better comment marker in Autoconf input

Use better comment marker in Autoconf input

The comment marker "#" is copied to the output, so it's only
appropriate for comments that make sense in the shell output.  For
comments about the Autoconf language, "dnl" should be used.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/4446565d36ac4482282146a9ab35068f18dff4fd

Modified Files
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config/llvm.m4     |  2 +-
config/programs.m4 |  2 +-
configure          |  9 +--------
configure.in       | 12 ++++++------
4 files changed, 9 insertions(+), 16 deletions(-)