zlib: properly split patches

This package had two patches (with two headers etc.) in one file,
which would have quilt merging them during a refresh.

Separate these patches into two files, as the original intent seems
to be having them separate.

Signed-off-by: Adrian Schmutzler <freifunk@adrianschmutzler.de>

package/libs/zlib/patches/005-relative-pkg-config-paths.patch

@@ -0,0 +1,14 @@
+--- a/zlib.pc.cmakein
++++ b/zlib.pc.cmakein
+@@ -1,8 +1,8 @@
+ prefix=@CMAKE_INSTALL_PREFIX@
+ exec_prefix=@CMAKE_INSTALL_PREFIX@
+-libdir=@INSTALL_LIB_DIR@
+-sharedlibdir=@INSTALL_LIB_DIR@
+-includedir=@INSTALL_INC_DIR@
++libdir=${exec_prefix}/lib
++sharedlibdir=${exec_prefix}/lib
++includedir=${prefix}/include
+ 
+ Name: zlib
+ Description: zlib compression library