freeimage improvements

1) use SOVERSION (don't hardcode library versions in plists)
2) use pre-configure over post-patch (good practice)
3) only .so files stay in dev*

* that's the current standard
  It's not perfect because sometimes configuration scripts assume that
  if .so is there, the symlinked target is also there.  In reality .so
  files should be separate from both dev and primary subpackages but
  that is too cumbersome.

  so the result is sometimes the port has to physically remove the file
  after installation.  Maybe rvn can be modified to help here?

bucket_F6/freeimage/manifests/plist.dev

@@ -2,8 +2,6 @@ include/FreeImage.h
 include/FreeImagePlus.h
 lib/libfreeimage.a
 lib/libfreeimage.so
-lib/libfreeimage.so.3
 lib/libfreeimageplus.a
 lib/libfreeimageplus.so
-lib/libfreeimageplus.so.3
 lib/pkgconfig/freeimage.pc

bucket_F6/freeimage/manifests/plist.primary

@@ -1,2 +1,4 @@
-lib/libfreeimage-3.18.0.so
-lib/libfreeimageplus-3.18.0.so
+lib/libfreeimage-%%SOVERSION%%.so
+lib/libfreeimage.so.%%SOMAJOR%%
+lib/libfreeimageplus-%%SOVERSION%%.so
+lib/libfreeimageplus.so.%%SOMAJOR%%

bucket_F6/freeimage/specification

@@ -1,5 +1,6 @@
 DEF[PORTVERSION]=	3.18.0
 DEF[DISTVERSION]=	3180
+DEF[SOVERSION]=		3.18.0
 # ----------------------------------------------------------------------------
 
 NAMEBASE=		freeimage
@@ -53,8 +54,9 @@ SUB_LIST=		VERSION="${PORTVERSION}"
 CFLAGS=			-std=c++14 -DPNG_ARM_NEON_OPT=0 -fexceptions -fvisibility=hidden -fPIC
 CXXFLAGS=		-std=c++14 -DPNG_ARM_NEON_OPT=0 -fexceptions -fvisibility=hidden -fPIC
 MAKE_ARGS=		CC="{{CC}}" CPP="{{CPP}}" CXX="{{CXX}}"
+SOVERSION=		${SOVERSION}
 
-post-patch:
+pre-configure:
 		${REINPLACE_CMD} -e 's|/usr|${PREFIX}| ; s|-o root -g root || ; \
 			/^-fPIC/d' ${WRKSRC}/Makefile.gnu ${WRKSRC}/Makefile.fip