allow override of Windows static lib name

* also changed name back to original default of yaml, as the change in #10 to `yaml_static` broke things that relied on that

CMakeLists.txt

@@ -8,6 +8,7 @@
 set (YAML_VERSION_STRING "${YAML_VERSION_MAJOR}.${YAML_VERSION_MINOR}.${YAML_VERSION_PATCH}")
 
 option(BUILD_SHARED_LIBS "Build libyaml as a shared library" OFF)
+option(YAML_STATIC_LIB_NAME "base name of static library output" yaml)
 
 #
 # Output directories for a build tree
@@ -56,7 +57,7 @@
 
 if(NOT BUILD_SHARED_LIBS)
   set_target_properties(yaml
-    PROPERTIES OUTPUT_NAME yaml_static
+    PROPERTIES OUTPUT_NAME ${YAML_STATIC_LIB_NAME}
   )
 endif()