Fix @param names in synchronized_value

[karpovantonme]

Thirteen @param tags in synchronized_value.hpp that do not match the parameters below them. Documentation only, no code touched.

The first parameter is called val, the comments say value

/**
 * @param value constant reference of the value to protect.
 * @param mtx reference to the mutex used to protect the value.
 */
const_strict_lock_ptr(T const& val, Lockable & mtx) :

Same in strict_lock_ptr, const_unique_lock_ptr and unique_lock_ptr.

Worth noting because it makes the fix less obvious than it looks: the name is not consistent in the file itself. unique_lock_ptr takes value in its three tag constructors and val in the plain one, so the comments are already correct in some places and wrong in others. I changed only the ones where the code says val and left the rest alone.

The other way round would work too: rename the parameters to value everywhere and leave every comment as it is. That touches declarations rather than comments, so I did not want to decide it on your behalf. Say the word and I will send that version instead.

@param tag on an unnamed parameter

/**
 * @param tag of type adopt_lock_t used to differentiate the constructor.
 */
unique_lock_ptr(T & value, Lockable & mtx, adopt_lock_t) BOOST_NOEXCEPT

The third argument has no name, and Doxygen cannot attach a @param to one. Naming it would go against the rest of the file, where every tag argument is unnamed, so those six lines became @note and say the same thing.

Both kinds are what clang -Wdocumentation reports as parameter '...' not found in the function declaration.