Automate the maintenance of SO_MINOR_VERSION for our shared libraries.

Up to now we've manually adjusted these numbers in several different
Makefiles at the start of each development cycle.  While that's not
much work, it's easily forgotten, so let's get rid of it by setting
the SO_MINOR_VERSION values directly from $(MAJORVERSION).

In the case of libpq, this dev cycle's value of SO_MINOR_VERSION happens
to be "10" anyway, so this switch is transparent.  For ecpg's shared
libraries, this will result in skipping one or two minor version numbers
between v9.6 and v10, which seems like no big problem; and it was a bit
inconsistent that they didn't have equal minor version numbers anyway.

Discussion: <21969.1471287988@sss.pgh.pa.us>

src/interfaces/ecpg/compatlib/Makefile

@@ -16,7 +16,7 @@ include $(top_builddir)/src/Makefile.global
 PGFILEDESC = "ECPG compat - compatibility library for ECPG"
 NAME= ecpg_compat
 SO_MAJOR_VERSION= 3
-SO_MINOR_VERSION= 9
+SO_MINOR_VERSION= $(MAJORVERSION)
 
 override CPPFLAGS := -I../include -I$(top_srcdir)/src/interfaces/ecpg/include \
 	-I$(libpq_srcdir) -DFRONTEND $(CPPFLAGS)

src/interfaces/ecpg/ecpglib/Makefile

@@ -16,7 +16,7 @@ include $(top_builddir)/src/Makefile.global
 PGFILEDESC = "ECPG - embedded SQL in C"
 NAME= ecpg
 SO_MAJOR_VERSION= 6
-SO_MINOR_VERSION= 9
+SO_MINOR_VERSION= $(MAJORVERSION)
 
 override CPPFLAGS := -I../include -I$(top_srcdir)/src/interfaces/ecpg/include \
 	-I$(libpq_srcdir) -I$(top_builddir)/src/port -DFRONTEND $(CPPFLAGS)

src/interfaces/ecpg/pgtypeslib/Makefile

@@ -16,7 +16,7 @@ include $(top_builddir)/src/Makefile.global
 PGFILEDESC = "pgtypes - library for data type mapping"
 NAME= pgtypes
 SO_MAJOR_VERSION= 3
-SO_MINOR_VERSION= 8
+SO_MINOR_VERSION= $(MAJORVERSION)
 
 override CPPFLAGS := -I../include -I$(top_srcdir)/src/interfaces/ecpg/include \
 	-DFRONTEND $(CPPFLAGS)

src/interfaces/libpq/Makefile

@@ -17,7 +17,7 @@ include $(top_builddir)/src/Makefile.global
 # shared library parameters
 NAME= pq
 SO_MAJOR_VERSION= 5
-SO_MINOR_VERSION= 10
+SO_MINOR_VERSION= $(MAJORVERSION)
 
 override CPPFLAGS :=  -DFRONTEND -DUNSAFE_STAT_OK -I$(srcdir) $(CPPFLAGS) -I$(top_builddir)/src/port -I$(top_srcdir)/src/port
 ifneq ($(PORTNAME), win32)