pgsql: Fix incorrect logic in JSON number lexer

Fix incorrect logic in JSON number lexer

Detectable by gcc -Wlogical-op.

Add two regression test cases that would previously allow incorrect
values to pass.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/f1f6737e154f9d00f1565fc08fd7ac677b380822

Modified Files
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src/backend/utils/adt/json.c       |    4 ++--
src/test/regress/expected/json.out |   10 ++++++++++
src/test/regress/sql/json.sql      |    2 ++
3 files changed, 14 insertions(+), 2 deletions(-)