Modified the CMakeLists.txt so that the developer could specify the location of SpiderMonkey.
Modified the CMakeLists.txt so that the developer could specify the location
of SpiderMonkey.

Note: This is not the final version. We should add some code to check the
location of SpiderMonkey automatically first.

ericmckean/google-gadgets-for-linux,ericmckean/google-gadgets-for-linux,pombreda/google-gadgets-for-linux,suzhe/google-gadgets-for-linux,pombreda/google-gadgets-for-linux,pombreda/google-gadgets-for-linux,suzhe/google-gadgets-for-linux,tectronics/google-gadgets-for-linux,suzhe/google-gadgets-for-linux,tectronics/google-gadgets-for-linux,GoogleCodeArchive/google-gadgets-for-linux,tectronics/google-gadgets-for-linux,GoogleCodeArchive/google-gadgets-for-linux,suzhe/google-gadgets-for-linux,ericmckean/google-gadgets-for-linux,ericmckean/google-gadgets-for-linux,GoogleCodeArchive/google-gadgets-for-linux,pmateti/google-gadgets-for-linux,GoogleCodeArchive/google-gadgets-for-linux,tectronics/google-gadgets-for-linux,pmateti/google-gadgets-for-linux,pmateti/google-gadgets-for-linux,pmateti/google-gadgets-for-linux,pombreda/google-gadgets-for-linux