build: unify mesa version by using a VERSION file

Rather than having to keep track of all the build systems and their respecitve
definition of the mesa version, use a single top file VERSION. Every build
system is responsible for reading/parsing the file and using it

v2:
* remove useless bulletpoint from the documentation, suggested by Matt
* "Androing is Linux. Use '/' in stead of '\'", spotted by Chad V
* use cleaner code to get the version in scons, suggested by Chad V

v3:
* ensure leading and trailing whitespace characters are stripped while parsing
* android: handle GNU shell commands approapriately

Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Chad Versace <chad.versace@linux.intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>

Android.common.mk

@@ -33,9 +33,10 @@ endif
 LOCAL_C_INCLUDES += \
 	$(MESA_TOP)/include
 
+MESA_VERSION=$(shell cat $(MESA_TOP)/VERSION)
 # define ANDROID_VERSION (e.g., 4.0.x => 0x0400)
 LOCAL_CFLAGS += \
-	-DPACKAGE_VERSION=\"9.3.0-devel\" \
+	-DPACKAGE_VERSION=\"$(MESA_VERSION)\" \
 	-DPACKAGE_BUGREPORT=\"https://bugs.freedesktop.org/enter_bug.cgi?product=Mesa\" \
 	-DANDROID_VERSION=0x0$(MESA_ANDROID_MAJOR_VERSION)0$(MESA_ANDROID_MINOR_VERSION)