gdb, gdbserver, gdbsupport: trim trailing whitespaces

I noticed my IDE (VSCode) starting to automatically trim trailing
whitespaces on save, despite the setting for it being disabled.  I
realized that this is because the .editorconfig file now has

    trim_trailing_whitespace = true

for many file types.  If we have this EditorConfig setting forcing
editors to trim trailing whitespaces, I think it would make sense to
clean up trailing whitespaces from our files.  Otherwise, people will
always get spurious whitespace changes when editing these files.

I did a mass cleanup using this command:

$ find gdb gdbserver gdbsupport -type f \( \
    -name "*.c" -o \
    -name "*.h" -o \
    -name "*.cc" -o \
    -name "*.texi" -o \
    -name "*.exp" -o \
    -name "*.tcl" -o \
    -name "*.py" -o \
    -name "*.s" -o \
    -name "*.S" -o \
    -name "*.asm" -o \
    -name "*.awk" -o \
    -name "*.ac" -o \
    -name "Makefile*" -o \
    -name "*.sh" -o \
    -name "*.adb" -o \
    -name "*.ads" -o \
    -name "*.d" -o \
    -name "*.go" -o \
    -name "*.F90" -o \
    -name "*.f90" \
\) -exec sed -ri 's/[ \t]+$//' {} +

I then did an autotools regen, because we don't actually want to change
the Makefile and Makefile.in files that are generated.

Change-Id: I6f91b83e3b8c4dc7d5d51a2ebf60706120efe691

gdb/break-catch-throw.c

@@ -366,11 +366,11 @@ handle_gnu_v3_exceptions (int tempflag, std::string &&except_rx,
 
 /* Look for an "if" token in *STRING.  The "if" token must be preceded
    by whitespace.
-   
+
    If there is any non-whitespace text between *STRING and the "if"
    token, then it is returned in a newly-xmalloc'd string.  Otherwise,
    this returns NULL.
-   
+
    STRING is updated to point to the "if" token, if it exists, or to
    the end of the string.  */