ucode: update to latest Git HEAD

ucode: update to latest Git HEAD

4ae7072 fs: use `getline()` for line wise read operations
21ace5e lexer: fixes for regex literal parsing
00965fa lib: implement slice() function
76d396d main: implement print mode
7bbba78 compiler: optimize function return opcode generation
a45f2a3 lexer: improve regex literal handling
d64d5d6 vm: maintain export symbol tables per program
f4b4ded uloop: task: gracefully handle absent output callback
a58fe47 ubus: hold reference to underlying connection until deferred is concluded
e23b58a lib: uc_system(): retry waitpid() on EINTR

Signed-off-by: Jo-Philipp Wich <jo@mein.io>