Issue #18: Test integer conversion in headers

https://github.com/alobbs/libhpack/issues/18

According to the draft there are several concerns regarding the VLQ
integer representation as explained in section **5. Security
Considerations**.

These 3 new tests verify that those concerns are addressed.

Integer concerns:
- size of integers in value: function indexed_big_value
- size of integers in encoded length: function indexed_many_zeroes

They also test that a very large, and incorrect, length value will not
break the library (function: literal_w_index_false_len).
Issue #18: Test integer conversion in headers

https://github.com/alobbs/libhpack/issues/18

There was an error in the comments of function *literal_w_index_false_len*
This has now been amended.
Issue #26: New integer tests

https://github.com/alobbs/libhpack/issues/26

There were several important cases that were not tested by *integer_test.c*

Added tests:
- *decode_too_big_for_int*: Decodes a number > INT_MAX
- *decode_too_big_for_uint*: Tries to decode a number > UINT_MAX
- *decode_too_big_for_ulong*: Tries to decode a number > ULONG_MAX
- *en_decode_max_uint_5bits*: Encode/Decode INT_MAX with 5 bit prefix
- *en_decode_2nd_byte_0*: Encode a number with 1st byte 1s and 2nd 0s
- *decode_too_many_zeros*: Tries to decode a number with too many zeros

Most of these tests fail with the current integer encoding/decoding
algoritm.
Fix #26: New VLQ integer encoding/decoding

https://github.com/alobbs/libhpack/issues/26

Encoding would encode numbers greater than INT_MAX.
Now it can enconde up to UINT_MAX.

Decoding would have trouble with:
- Numbers greater than INT_MAX --> Return negative number
- Numbers greater than UINT_MAX
- Would process all bytes of a stream with many zeros

According to the draft if we encounter too big a number or too many
zeros in the encoding we should consider this an error. Now it does.
Fix #26: integer.h amends

https://github.com/alobbs/libhpack/issues/26

Changes to integer.h:
- Removed *MIN macro*
- Renamed *MAX_LEN_INTEGER* to *VLQ_MAX_LEN_INTEGER*
Merge pull request #27 from Akrog/header_test

Issue #18: Test integer conversion in headers

According to the draft there are several concerns regarding the VLQ
integer representation as explained in section 5. Security
Considerations.

These 3 new tests verify that those concerns are addressed.

Integer concerns:

size of integers in value: function indexed_big_value
size of integers in encoded length: function indexed_many_zeroes
They also test that a very large, and incorrect, length value will not
break the library (function: literal_w_index_false_len).
Fix #26: integer.c amends

https://github.com/alobbs/libhpack/issues/26

Changes to integer.c:
- Renamed *MAX_LEN_INTEGER* to *VLQ_MAX_LEN_INTEGER*
Merge pull request #28 from Akrog/integer_fix2

Issue #26: New integer tests

There were several important cases that were not tested by integer_test.c

Added tests:

decode_too_big_for_int: Decodes a number > INT_MAX
decode_too_big_for_uint: Tries to decode a number > UINT_MAX
decode_too_big_for_ulong: Tries to decode a number > ULONG_MAX
en_decode_max_uint_5bits: Encode/Decode INT_MAX with 5 bit prefix
en_decode_2nd_byte_0: Encode a number with 1st byte 1s and 2nd 0s
decode_too_many_zeros: Tries to decode a number with too many zeros
Most of these tests fail with the current integer encoding/decoding
algoritm.
New method

Implements hpack_header_field_is_empty()
Fix #29: Issues linking to check

https://github.com/alobbs/libhpack/issues/29

It has been detected that when pkg-config is not installed on the
machine you will get a series of linking errors:

```
Linking C executable test_libchula
cd /home/akrog/Web/Teamwork/libhpack/build/libchula/test && /usr/bin/cmake -E cmake_link_script CMakeFiles/test_libchula.dir/link.txt --verbose=1
/usr/bin/cc      CMakeFiles/test_libchula.dir/avl_test.c.o CMakeFiles/test_libchula.dir/main.c.o CMakeFiles/test_libchula.dir/list_test.c.o CMakeFiles/test_libchula.dir/util_test.c.o CMakeFiles/test_libchula.dir/buffer_test.c.o CMakeFiles/test_libchula.dir/missing_sysfuncs_
test.c.o CMakeFiles/test_libchula.dir/md5_test.c.o  -o test_libchula -rdynamic ../libchula.a
```

That is because cmake is piggybacking on pkg-config for the resolution
of *pkg_check_modules(CHECK check)* and since there is no pkg-config it
cannot do the search.

I believe we should set pkg-config and check as REQUIRED in cmake so
that the compilation stops as soon as this is detected.

This solution will work fine (it will compile correctly) if there is no
pkg-config but we have selected BUILD_TESTS=OFF in the Makefile.
Add the missing include and fix #23
Add the missing includes and fix #22
Renames imported code
const unsigned char* should be const char*

chula_buffer_t is a char *buf;
utf8_get_next_char returns const char *
should make s, s_next both const char *
Fixes compilation in OSX
Merge pull request #32 from skinkie/fix_issue_31

const unsigned char* should be const char*
Extends a QA test

Adds a third request to one of the series.
Merge branch 'master' of github.com:alobbs/libhpack
Fixes a few compilation warnings
Bug fix

Fixes a copy & paste mistake. The sys/ioctl.h header was not being
detected correctly.