build: increment API_VERSION after release

With v2.5.0 out, increment API_VERSION, so binaries dynamically linked
against the released raylib aren't accidentally paired with a development
or later released raylib that may be incompatible.

src/CMakeLists.txt

@@ -4,7 +4,7 @@ include(GNUInstallDirs)
 list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../cmake")
 
 set(PROJECT_VERSION 2.5.0)
-set(API_VERSION 2)
+set(API_VERSION 251)
 
 include("CMakeOptions.txt")
 include(BuildType)

src/Makefile

@@ -43,7 +43,7 @@
 
 # Define required raylib variables
 RAYLIB_VERSION     = 2.5.0
-RAYLIB_API_VERSION = 2
+RAYLIB_API_VERSION = 251
 
 # See below for alternatives.
 RAYLIB_PATH        = ..