HP-UX (all versions) requires shared libraries to have execute
permission, and really needs them to be exactly mode 555 for
performance reasons.  The standard configure/install procedure
installs libpq.sl as mode 644, which DOES NOT WORK.

The attached patch modifies the makefiles to distinguish
INSTL_LIB_OPTS (install mode for ordinary libraries) from
INSTL_SHLIB_OPTS (mode for shared libs), and adds a test
to configure to set INSTL_SHLIB_OPTS="-m 555" when on HP-UX.