String parsing example in CVC parser
add negative int2str
Merge branch 'master' of github.com:tiliang/CVC4
String parsing example in CVC parser
add negative int2str
hot fix for str2int/int2str
Merge branch 'master' of github.com:tiliang/CVC4

Conflicts:
	src/theory/strings/theory_strings_preprocess.cpp
String parsing example in CVC parser
add negative int2str
hot fix for str2int/int2str
Merge branch 'master' of github.com:tiliang/CVC4

Conflicts:
	src/theory/strings/theory_strings_preprocess.cpp
add two cases to the regression test
add more tests, and define int.to.str(NEGATIVE)=""
fix makefile