I was looking at an issue with ogr_fdw where it is trying to get the PG_VERSION_NUM when I noticed that in Postgresql 10.1 this is declared as:
#define PG_VERSION_NUM 100001
But shouldn't it be
#define PG_VERSION_NUM 100100
or am I being dense, in which case sorry to have bothered you.
Beginning with v10 the middle two digits with ALWAYS be zero - only the first two (major release) and last two (patch version) are changed. 10.1 means v10 with the first patch release, unless 9.6 which is a major version in its own right and, with patch version, reads 9.6.3
