[flow] vm: program pretty-print update

Change-Id: I2b6f62643814854c8c337238c799121227f8dd52
updates

Change-Id: I12639aba901f7f17f113237da481df10cbf5ef7e
[base] Buffer API improvements (work-in-progress)

Change-Id: I1d6b993a3b3a827f87addbd86af867699657778e
[flow] experimental work on an SSA-form based IR

Change-Id: I1ae71432d7dffa7b9f5bb4c2dc8586f423522a0e
fixes

Change-Id: Iaf44387777fdd4e6df1fd695752f172cb762e2a9
[flow] vm: implements SREGMATCH

Change-Id: I9ee274dc2456f90e445390b872e45f96550f9a65
[base] Buffer: implements missing find(BufferRef)

Change-Id: I0979efcadde0b5f7c64d929d151e5999752ffe1e
[base] Buffer: adds reverse iterator

Change-Id: Ia2897be2b01fac0966c0ca8cfc7c8308054e8cb7
[flow] vm: more work on moving from std::string to BufferRef as FlowString

Change-Id: I47ec9504e20a7b20621afaa7fb071c41d9558b17