Remove use of whole-archive (#677)

* Add source files wrapper library

Allow to not archive HAL/LL object files to core.a.
This avoid the linker to select weak definitions instead
of non-weak ones when 'whole-archive' option is not used.

See:
 http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka15833.html

* Remove use of whole-archive

* Move newlib syscall implementation outside core archive

Due to a bug in the arm none eabi gcc with lto which raise
an unresolved reference if syscall is in the archive (_sbrk,...)

Author: fpistm

libraries/SrcWrapper/keywords.txt

@@ -0,0 +1,15 @@
+#######################################
+# Syntax Coloring Map For SrcWrapper
+#######################################
+
+#######################################
+# Datatypes (KEYWORD1)
+#######################################
+
+#######################################
+# Methods and Functions (KEYWORD2)
+#######################################
+
+#######################################
+# Constants (LITERAL1)
+#######################################

libraries/SrcWrapper/library.properties

@@ -0,0 +1,9 @@
+name=Source Wrapper
+version=1.0.0
+author=Frederic Pillon
+maintainer=stm32duino
+sentence=Source files wrapper (HAL, LL,...)
+paragraph=Allow to not archive source object files to core.a. This avoid the linker to select weak definitions instead of non-weak ones when 'whole-archive' option is not used.
+category=Other
+url=
+architectures=stm32