Add a missing library for compiling on GNU/Linux

I've added "-ldl" library, it's necessary to compile the project.

examples/makefile

@@ -126,7 +126,7 @@ ifeq ($(PLATFORM),PLATFORM_DESKTOP)
         # libraries for Debian GNU/Linux desktop compiling
         # requires the following packages:
         # libglfw3-dev libopenal-dev libglew-dev libegl1-mesa-dev
-        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread
+        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread -ldl
 	# on XWindow could require also below libraries, just uncomment
 	#LIBS += -lX11 -lXrandr -lXinerama -lXi -lXxf86vm -lXcursor
     else

templates/advance_game/makefile

@@ -151,7 +151,7 @@ ifeq ($(PLATFORM),PLATFORM_DESKTOP)
         # libraries for Debian GNU/Linux desktop compiling
         # requires the following packages:
         # libglfw3-dev libopenal-dev libglew-dev libegl1-mesa-dev
-        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread
+        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread -ldl
         # on XWindow could require also below libraries, just uncomment
         #LIBS += -lX11 -lXrandr -lXinerama -lXi -lXxf86vm -lXcursor
     else

templates/basic_game/makefile

@@ -129,7 +129,7 @@ ifeq ($(PLATFORM),PLATFORM_DESKTOP)
         # libraries for Debian GNU/Linux desktop compiling
         # requires the following packages:
         # libglfw3-dev libopenal-dev libglew-dev libegl1-mesa-dev
-        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread
+        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread -ldl
         # on XWindow could require also below libraries, just uncomment
         #LIBS += -lX11 -lXrandr -lXinerama -lXi -lXxf86vm -lXcursor
     else

templates/basic_test/makefile

@@ -128,9 +128,9 @@ ifeq ($(PLATFORM),PLATFORM_DESKTOP)
         # libraries for Debian GNU/Linux desktop compiling
         # requires the following packages:
         # libglfw3-dev libopenal-dev libglew-dev libegl1-mesa-dev
-        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread
+        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread -ldl
         # on XWindow could require also below libraries, just uncomment
-        #LIBS += -lX11 -lXrandr -lXinerama -lXi -lXxf86vm -lXcursor 
+        #LIBS += -lX11 -lXrandr -lXinerama -lXi -lXxf86vm -lXcursor
     else
     ifeq ($(PLATFORM_OS),OSX)
         # libraries for OS X 10.9 desktop compiling

templates/simple_game/makefile

@@ -129,7 +129,7 @@ ifeq ($(PLATFORM),PLATFORM_DESKTOP)
         # libraries for Debian GNU/Linux desktop compiling
         # requires the following packages:
         # libglfw3-dev libopenal-dev libglew-dev libegl1-mesa-dev
-        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread
+        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread -ldl
         # on XWindow could require also below libraries, just uncomment
         #LIBS += -lX11 -lXrandr -lXinerama -lXi -lXxf86vm -lXcursor
     else

templates/standard_game/makefile

@@ -129,7 +129,7 @@ ifeq ($(PLATFORM),PLATFORM_DESKTOP)
         # libraries for Debian GNU/Linux desktop compiling
         # requires the following packages:
         # libglfw3-dev libopenal-dev libglew-dev libegl1-mesa-dev
-        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread
+        LIBS = -lraylib -lglfw3 -lGLEW -lGL -lopenal -lm -pthread -ldl
         # on XWindow could require also below libraries, just uncomment
         #LIBS += -lX11 -lXrandr -lXinerama -lXi -lXxf86vm -lXcursor
     else