doc(README.md): add pkg-config

[skip ci]
doc(ubuntu-gcc.md): add pkg-config

[skip ci]
doc(ubuntu-clang.md): add pkg-config

[skip ci]
src(tools/simple-bmc): add Makefile, update _tags
src(tools/simple-bmc): add Integral and Vec to exp, simplify code
src(tools/simple-bmc): update Define-ODE to take a set of ODEs
src(tools/simple-bmc): use new define-ODE and produce flow formula(integral)
fix(tools/simple-bmc): update makefile
feat(tools/simple-bmc): print define-ode using prefix format
fix(bmc.ml): add mode flow for final step
feat(DSL/): add parsing code for basic construct
feat(DSL/): most parsing working
fix(DSL/): fix proceed expression & assignment expression
fix(DSL/): add b_var & assert expression
fix(parser.mly): function application should be expression, not
statement
fix(parse.mly, lexer.mll): arguments for function application should be
\ expression
fix(type.ml, parser,mly): merge If1 and If2.
feat(invariant-checking): basic skeleton
fix(invariant-checking): fix data file bug, fix typo
fix(inv_checking.ml): generate final formula