Improve documentation to latest changes

doc/mrbgems/README.md

@@ -33,8 +33,8 @@ All GEMs have to be located under *$(MRUBY_ROOT)/mrbgems/g/*.
 ## Build process
 
 mrbgems will call *make* to build and *make clean* to clean your GEM. You
-have to build a *gem.a* file during this build process. How you are going
-to do this is up to you.
+have to build a *mrb-GEMNAME-gem.a* file during this build process. How you
+are going to do this is up to you.
 
 To make your build process more easier and more standardized we suggest
 to include *mrbgems/Makefile4gem* which defines some helper rules. In
@@ -52,8 +52,8 @@ The *Makefile* is used for building a C extension. You should
 define *GEM* (GEM name), *GEM_C_FILES* (all C files) and
 *GEM_OBJECTS* (all Object files). Pay also attention that your
 *Makefile* has to build the object files. You can use
-*gem-c-files* to build a *gem.a* out of your Object code and use
-*gem-clean-c-files* to clean the object files.
+*gem-c-files* to build a *mrb-GEMNAME-gem.a* out of your
+Object code and use *gem-clean-c-files* to clean the object files.
 
 ### Pre-Conditions
 
@@ -100,7 +100,7 @@ folder.
 
 The *Makefile* is used for building a Ruby extension. You should  define
 *GEM* (GEM name) and *GEM_RB_FILES* (all Ruby files). You can use
-*gem-rb-files* to build a *gem.a* out of your Ruby code and use
+*gem-rb-files* to build a *mrb-GEMNAME-gem.a* out of your Ruby code and use
 *gem-clean-rb-files* to clean the generated C files.
 
 ### Pre-Conditions
@@ -137,8 +137,9 @@ into the *mrblib* folder and all C files into the *src* folder.
 The *Makefile* is used for building a C and Ruby extension. You should
 define *GEM* (GEM name), *GEM_C_FILES* (all C files), *GEM_OBJECTS*
 (all Object files) and *GEM_RB_FILES* (all Ruby files). You can use
-*gem-c-and-rb-files* to build a *gem.a* out of your Object and Ruby code
-and use *gem-clean-c-and-rb-files* to clean the generated C files.
+*gem-c-and-rb-files* to build a *mrb-GEMNAME-gem.a* out of your Object
+and Ruby code. Use *gem-clean-c-and-rb-files* to clean the generated
+C files. 
 
 ### Pre-Conditions