build: support versioned dependencies

Makefile

@@ -26,7 +26,7 @@ $(eval $(call find_bin,doxygen))
 $(eval $(call find_bin,sphinx-build))
 $(eval $(call find_bin,gccgo))
 $(eval $(call find_python))
-$(eval $(call find_lib,libmemcached))
+$(eval $(call find_lib,libmemcached,1.0))
 
 # Work around luajit on OS X
 ifeq ($(PLATFORM), Darwin)

platform.mk

@@ -81,16 +81,21 @@ endef
 
 # Find library (pkg-config)
 define find_lib
-	$(call find_alt,$(1),$(1))
+	$(call find_alt,$(1),$(1),$(2))
 endef
 
 # Find library alternative (pkg-config)
 define find_alt
 	ifeq ($$(strip $$($(1)_LIBS)),)
-		$(1)_CFLAGS := $(shell pkg-config --cflags $(2) --silence-errors)
-		$(1)_LIBS := $(shell pkg-config --libs $(2)  --silence-errors)
+		ifneq ($(strip $(3)),)
+			$(1)_VER := $(shell pkg-config --atleast-version=$(3) $(2) && echo $(3))
+		endif
+		ifeq ($(strip $(3)),$$($(1)_VER))
+			$(1)_CFLAGS := $(shell pkg-config --cflags $(2) --silence-errors)
+			$(1)_LIBS := $(shell pkg-config --libs $(2)  --silence-errors)
+		endif
 	endif
-	$(call have_lib,$(1))
+	$(call have_lib,$(1),$(3))
 endef
 
 # Find binary