Add T4 bit map compression routines

Add bit map encoder and decoder functions: decoder is fully functional
while encoder is good enough for testing - no backtracking to find
the best possible compression is implemented. If somebody is willing to
implement MS side of EDGE than this has to be expanded.
Add corresponding tests.
N. B: the encoding is implemented according to ETSI TS 44.060 which is
slightly different from T4 used for fax according to CCITT G31D (RFC 804).

Ticket: OW#2407
Sponsored-by: On-Waves ehf

Signed-off-by: Max <msuraev@sysmocom.de>
diff --git a/tests/bits/bitcomp_test.ok b/tests/bits/bitcomp_test.ok
new file mode 100644
index 0000000..238f3c4
--- /dev/null
+++ b/tests/bits/bitcomp_test.ok
@@ -0,0 +1,29 @@
+
+running static tests...
+
+TEST1:
+ 00110111 01000111 10000001 1111
+ 00110111 01000111 10000001 1111
+Encoded:
+-1 00110111 01000111 10000001 1111 [28]
+Expected:
+0 11011110 10001000 01110101 01100101 100 [35]
+  11011110 10001000 01110101 01100101 100 [35]
+
+Decoded:
+0 00110111 01000111 10000001 1111 [28]
+Expected:
+  00110111 01000111 10000001 1111 
+
+TEST2:
+ 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 00000000 00
+ 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 00000000 00
+Encoded:
+1 11011101 01000001 00 [18]
+Expected:
+1 11011101 01000001 00 [18]
+
+Decoded:
+0 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 00000000 00 [90]
+Expected:
+  11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111111 00000000 00