Fixed PostgreSQL version matching after PG 10

Backport to psycopg 2.6 of ticket #489, ticket #632

NEWS

@@ -7,6 +7,8 @@ What's new in psycopg 2.6.3
 - Throw an exception trying to pass ``NULL`` chars as parameters
   (:ticket:`#420`).
 - Make `~psycopg2.extras.Range` objects picklable (:ticket:`#462`).
+- Fixed version parsing and building of PostgreSQL 10.
+  Fix backport for :tickets:`#489, #632`.
 
 
 What's new in psycopg 2.6.2

setup.py

@@ -415,13 +415,18 @@ class psycopg_build_ext(build_ext):
                 pgversion = "7.4.0"
 
             verre = re.compile(
-                r"(\d+)\.(\d+)(?:(?:\.(\d+))|(devel|(alpha|beta|rc)\d+))")
+                r"(\d+)(?:\.(\d+))?(?:(?:\.(\d+))|(devel|(?:alpha|beta|rc)\d+))?")
             m = verre.match(pgversion)
             if m:
                 pgmajor, pgminor, pgpatch = m.group(1, 2, 3)
+                # Postgres >= 10 doesn't have pgminor anymore.
+                pgmajor = int(pgmajor)
+                if pgmajor >= 10:
+                    pgminor, pgpatch = None, pgminor
+                if pgminor is None or not pgminor.isdigit():
+                    pgminor = 0
                 if pgpatch is None or not pgpatch.isdigit():
                     pgpatch = 0
-                pgmajor = int(pgmajor)
                 pgminor = int(pgminor)
                 pgpatch = int(pgpatch)
             else: