libpbc: Pass CFLAGS properly

This was breaking ASLR builds.

Fixed license tag.

Added PKG_BUILD_PARALLEL for faster compilation.

Small Makefile cleanups.

Signed-off-by: Rosen Penev <rosenp@gmail.com>
(cherry-picked from 43f811ad5b)

libs/libpbc/patches/010-pass-cflags.patch

@@ -0,0 +1,10 @@
+--- a/configure.ac
++++ b/configure.ac
+@@ -10,7 +10,6 @@ AC_CONFIG_SRCDIR([./])
+ LT_INIT
+ #AC_CANONICAL_HOST
+ 
+-CFLAGS=
+ default_fink_path=/sw
+ case $host_os in
+      darwin*)