Fix location of pgtcl package and generation of linker flags.
See also issue #39.
Merge pull request #41 from gahr/fix-ld-flag

Fix location of pgtcl package and generation of linker flags.
Apply the fix in #41 at the m4 level
Merge pull request #42 from gahr/fix-ld-flag-2

Apply the fix in #41 at the m4 level
Merge branch 'master' into cpp