Fix parallel make when running make install before make all

In addition to the

all-foo-recurse: all-bar-recurse

dependencies that constraint the order of the rule execution, we need

install-foo-recurse: install-bar-recurse

dependencies in case one runs make install without a make all first,
as some people apparently do.

src/interfaces/Makefile

@@ -17,3 +17,4 @@ SUBDIRS = libpq ecpg
 $(recurse)
 
 all-ecpg-recurse: all-libpq-recurse
+install-ecpg-recurse: install-libpq-recurse

src/interfaces/ecpg/Makefile

@@ -8,6 +8,8 @@ $(recurse)
 
 all-compatlib-recurse: all-ecpglib-recurse
 all-ecpglib-recurse: all-pgtypeslib-recurse
+install-compatlib-recurse: install-ecpglib-recurse
+install-ecpglib-recurse: install-pgtypeslib-recurse
 
 clean distclean maintainer-clean:
 	$(MAKE) -C test clean