Revert changes relative to lib/*.[ch] recent renaming

This reverts renaming and usage of lib/*.h header files done
28-12-2012, reverting 2 commits:

f871de0... build: make use

Revert changes relative to lib/*.[ch] recent renaming

This reverts renaming and usage of lib/*.h header files done
28-12-2012, reverting 2 commits:

f871de0... build: make use of 76 lib/*.h renamed files
ffd8e12... build: rename 76 lib/*.h files

This also reverts removal of redundant include guard (redundant thanks
to changes in above commits) done 2-12-2013, reverting 1 commit:

c087374... curl_setup.h: remove redundant include guard

This also reverts renaming and usage of lib/*.c source files done
3-12-2013, reverting 3 commits:

13606bb... build: make use of 93 lib/*.c renamed files
5b6e792... build: rename 93 lib/*.c files
7d83dff... build: commit 13606bbfde follow-up 1

Start of related discussion thread:

http://curl.haxx.se/mail/lib-2013-01/0012.html

Asking for confirmation on pushing this revertion commit:

http://curl.haxx.se/mail/lib-2013-01/0048.html

Confirmation summary:

http://curl.haxx.se/mail/lib-2013-01/0079.html

NOTICE: The list of 2 files that have been modified by other
intermixed commits, while renamed, and also by at least one
of the 6 commits this one reverts follows below. These 2 files
will exhibit a hole in history unless git's '--follow' option
is used when viewing logs.

lib/curl_imap.h
lib/curl_smtp.h

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build: make use of 76 lib/*.h renamed files

76 private header files renamed to use our standard naming scheme.

This change affects 322 files in libcurl's source tree.

curl tool: make curl.h first header included in tool_setup.h

curl tool: use configuration files from lib directory

Configuration files such as curl_config.h and all config-*.h no longer exist
nor are generated/copied into 'src' directory, now thes

curl tool: use configuration files from lib directory

Configuration files such as curl_config.h and all config-*.h no longer exist
nor are generated/copied into 'src' directory, now these only exist in 'lib'
directory from where curl tool sources uses them.

Additionally old src/setup.h has been refactored into src/tool_setup.h which
now pulls lib/setup.h

The possibility of a makefile needing an include path adjustment exists.

show more ...

curl tool: reviewed code moved to tool_*.[ch] files

my_setopt and my_setopt_str no longer ignores curl_easy_setopt result.

Fixed some OOM handling issues.