Fix the following error:

ERROR: imagemagick6-dev*: usr/lib/pkgconfig/ImageMagick++-6.Q16.pc: pkgconf version 6.9.12-31 is invalid

See also https://github.com/ImageMagick/ImageMagick6/commit/442c4b225e78787b1b4c59af06343531eaa363fc

--- a/Magick++/lib/ImageMagick++.pc.in
+++ b/Magick++/lib/ImageMagick++.pc.in
@@ -7,7 +7,7 @@
  
 Name: ImageMagick++
 Description: Magick++ - C++ API for ImageMagick (ABI @MAGICK_ABI_SUFFIX@)
-Version: @PACKAGE_VERSION@
+Version: @PACKAGE_BASE_VERSION@
 Requires: MagickWand-@MAGICK_MAJOR_VERSION@.@MAGICK_ABI_SUFFIX@ 
 Libs: -L${libdir} -l${libname}
 Libs.private: -L${libdir} -l${libname} @MAGICK_LIBS@ @MATH_LIBS@
--- a/wand/Wand.pc.in
+++ b/wand/Wand.pc.in
@@ -8,7 +8,7 @@
 Name: MagickWand
 Description: MagickCore - C API for ImageMagick (ABI @MAGICK_ABI_SUFFIX@)
 URL: https://github.com/ImageMagick/ImageMagick6
-Version: @PACKAGE_VERSION@
+Version: @PACKAGE_BASE_VERSION@
 Requires: MagickCore
 Cflags: -I${includearchdir} -I${includedir} @MAGICK_PCFLAGS@
 Libs: -L${libdir} -l${libname}