documentation/sphinx: Fix formatting errors in .rst files

Fixes broken references to other documents/sections.
Moves remaining tutorials to the `mynewt-documentation` repository.

Author: wpiet

docs/os/modules/baselibc.rst

@@ -47,7 +47,7 @@ List of Functions
 
 Documentation for libc functions is available from multiple places. One
 example are the on-line manual pages at
-`https://www.freebsd.org/cgi/man.cgi <#https://www.freebsd.org/cgi/man.cgi>`__.
+`FreeBSD website <https://www.freebsd.org/cgi/man.cgi>`_.
 
 baselibc supports most libc functionality; malloc(), printf-family,
 string handling, and conversion routines.

docs/os/modules/hal/hal_i2c/hal_i2c.rst

@@ -13,8 +13,7 @@ board and often peripherals devices located off the circuit board.
 I2C is often though of as a 2-wire protocol because it uses two wires
 (SDA, SCL) to send data between devices.
 
-For a detailed description of I2C, see the `I²C wikipedia
-page <https://en.wikipedia.org/wiki/I²C>`__
+For a detailed description of I²C, see the `wikipedia page <https://en.wikipedia.org/wiki/I2C>`_
 
 HAL\_I2C Theory Of Operation
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~